Crosby, who played varsity basketball at Council Rock High School South, had served four years in the United States Marine Corps, with two tours in Iraq.
When he came home from war in late 2008, he soon faced another scourge - addiction to prescription pain medications. His life descended into another hell, one maybe worse than war.
He couldn't admit to himself, much less to his family, what he'd become. And now, on Jan. 24, 2013, the VA insisted that if he wanted to continue getting care, he needed to join its hardest cases at the methadone clinic.
He also was humiliated by the fact that methadone was dispensed into paper cups from behind bulletproof glass.
"I had a whole company of Marines looking up to me," he said. "And now I'm labeled as a junkie."
Did he have the strength to reclaim his life, to break free?
Prescription drug abuse is a national epidemic, says the Centers for Disease Control and Prevention, causing 15,000 overdose deaths a year.
In the last decade, prescriptions of addictive opiates in America climbed 300 percent, the CDC said.
The military did no better. In the 12 years after 9/11, prescriptions of four primary opiate painkillers - oxycodone, hydrocodone, morphine and methadone - rose 270 percent at VA hospitals, according to internal VA records obtained by the Center for Investigative Reporting.
Last year, 50,000 veterans were treated for addiction at all VA hospitals - one of whom was Crosby.
The oldest of seven, Crosby came from a close family in Holland, Pa. He was 6-4 and athletic. His senior year, 2004, he led the basketball team in taking offensive charges, foreshadowing his toughness, his willingness to sacrifice.
After high school, Crosby joined the Marines, believing it the ultimate test of his body and will. Almost immediately, his motivation changed. "As horrible as this might sound," he says, "I loved making men better, preparing them for war."
He flourished. At 19, in August 2005, on the way over for his first tour in Iraq, he was made a team leader. "That really scared me," he said. "They trusted me enough to have the lives of three guys underneath me."
He spent five months in Anbar province until February 2006. On his first patrol, sweeping the desert, he found a cache of 49 enemy land mines and a mortar. Two weeks later, when an Iraqi police officer was shot by a sniper, Crosby returned fire, then applied a tourniquet and an intravenous line, helping to save the man's life.
"Lance Corporal Crosby's professionalism, initiative and dedication to duty reflected credit upon him and were in keeping with the highest tradition," a Marine citation read.
After a year in North Carolina training Marines at Camp Lejeune, he went back to Anbar for another tour, from March to September 2007. That time he was a squad leader.
"The best advice I gave my guys," he said, "was, 'Try as much as you can to make it feel like a game. You take it personally, you're going to be screwed up the rest of your life.' I always told them, 'Blame it on me' when you thought about it because I made you do everything. I gave the orders."
When out on sweeps, he would wear a flak jacket with metal protective inserts front and back that weighed 25 pounds each. He'd also carry his M-16, 400 rounds of ammunition, food, water, and supplies.
He'd weigh himself on a grain scale at a market; gear was more than 100 pounds.
"One sweep was 85 kilometers," he said. "Another was 100 (62 miles), walking the entire time along the Euphrates River, just looking for munitions or waiting for somebody to shoot at us."
"Nothing prepares you for war," Crosby said.
After his company shot a suicide bomber, rather than remove the vest of explosives, they just detonated it on him, blowing up the dead body.
He searched bodies with faces blown off by .50-caliber rounds.
"We'd have to shoot dogs and light them on fire," he said. "They had a bunch of disease-ridden dogs. I tried my best not to shoot them, but we had orders to shoot every dog we saw. Douse them with diesel and light the fire so it doesn't spread disease. My first deployment, that messed me up more than people trying to kill me."
The first time Crosby can remember taking an opiate was when he got his front teeth knocked out by the buttstock of a machine gun on that first tour.
"We were chasing a vehicle," he recalled. "We made a turn and ... the turret came around and smacked me in the mouth."
After two weeks, he was off the opiate, back in action; he got temporary teeth on a Navy ship.
To VA doctors, he shared far worse.
"The descriptions of the things he suffered in the service were horrific," said Dave Oslin, chief of behavioral health at the Philadelphia VA Medical Center.
"There was the Humvee accident where some of his buddies got killed. He's in a Humvee, and it gets exploded. He was actually thrown out of the vehicle and knocked out. He probably has bad traumatic brain injury, but he's refused to get worked up.
"No doubt in my mind he has really bad PTSD, and really bad back pain," Oslin added. "So, yes, we screwed him up by sending him to a war zone. We, collectively, the country."
Crosby came home in fall 2008.
His back was in agony.
"On a scale of 1 to 10," he says, "it was an 11. I was crawling down my stairs in the morning to use the bathroom."
Emotionally, he was a mess.
Medical records show his own father, a contractor, fired Crosby from a job "due to irritability and conflict with co-workers."
One doctor wrote that Crosby "feels empty. He has lost the ability and desire to connect with people," adding: "He is hypervigilant. He carries a weapon around the home. He could not sleep without a loaded weapon under his bed for many months."
His father recalls those first months at home this way:
"I didn't think he was that bad. He would wake up in the middle of the night screaming. But that was once in a while. Then he went to the VA and he came back with these prescriptions, and I didn't know what they were. It was just like he wasn't there. He's just not doing anything. He was hard to talk to. He'd fall asleep all day. I think they gave him drugs he didn't need, at least not the way they gave them to him."
Crosby and his father see that as the VA making opiates easy to use, using them as a Band-Aid for his problems.
"I was a 22-year-old kid," he said. "What did I know? I figured they knew best."
Crosby says: "They gave me pain meds and they worked like a charm. I could walk and run again."
Oslin adds other details.
"He had clear positive drug screens for opiates before we started prescribing," Oslin said. Records say Crosby told doctors he took prescription drugs from his grandmother and they made him feel better.
Oslin said the VA faced a choice. Crosby had immense pain. He said the opiates from his grandmother were helping. So doctors started him on a course of opiates doctors thought they could manage. "We don't want him abusing," Oslin said. "Can we partner and do this better?"
Within six months, the VA was concerned about addiction, and after a year, doctors were certain of it, Oslin said.
"Most people who start on opiates do not get addicted," Oslin said. "The problem is we have no idea who is (prone) and who isn't. When you become addicted, it's a terrible path. So is that reason enough to never use these drugs? Probably not."
Crosby took engineering classes at Drexel University, and other classes at Bucks County Community College. But going to school and wrestling with addiction weren't compatible.
Crosby hated what was happening to him, the person he'd become. Typical for people in his condition, he made bad decisions; in his worst moments, he bought drugs illegally, even heroin.
Sometimes, he says, he'd buy them right at the VA, where dealers push product outside the methadone clinic. Crosby hated that you had to walk by a gantlet of dealers to reach the methadone clinic, and complained about it to his doctors many times. He also said he often waited an hour or more at the clinic - going there, waiting, getting home, took the whole morning.
Oslin says the VA is trying to change.
"There's a major effort now to systematically review patients on high-dose opiates and try to get them off," he said. "That's a very aggressive program. There's a lot more attention to trying not to do pharmacological treatments. Trying spinal blocks, physical therapy. A realization that opiates aren't the answer."
Oslin also said doctors heard complaints about drug dealers outside the methadone clinic and hated the situation as much as patients. He said he believed law enforcement did a pretty good job trying to control it with cameras, surveillance, and more.
"Any place that you have a methadone clinic," he said, "you're vulnerable to diversion, and you're vulnerable to dealers preying on the population."
By last August, Crosby had another catalyst for change. He was charged with DUI on Aug. 31 and spent the night in Philadelphia's Roundhouse, his first time in jail.
The case was referred to Philadelphia Veterans Court, set up to give special help and attention to veterans, to keep them out of jail, out of trouble. The arrest will vanish from his record if he completes therapy and treatment.
"The great thing about Pearson is that he has finally come to grips with that he does need help," said Michael Brown, a court coordinator. "I think that has allowed him to buy into some of the treatment that he's undertaking.
"I love Pearson. He's a great person. I have the full confidence that he can do it."
Crosby also began dating Kirsten Hagen, 24. They have known each other all their lives - their fathers are close friends who have worked together in the contracting business. She knew him before Iraq, before addiction.
Hagen is earning a master's degree in psychology at Rosemont College, and also getting a pilot's license.
She challenged him to imagine his life free of the drugs, the clinic, the crutch.
In the winter, Crosby started cutting back on his methadone - from 90-milligram daily doses to 20. He also gradually cut back on other medications he was taking, including Xanax.
In addition, he had been going to physical therapy for two years, and his back pain wasn't as bad.
He stumbled a few times.
"When he believed I no longer believed he could beat it - he did," Hagen said.
Crosby tried for a few weeks to do his final phase of detox as an inpatient at the VA, and got frustrated when they would make him wait all day, but then send him home.
Finally, he just decided to do it on his own. On March 18, he gave her his car keys. He locked down his bank accounts - just in case he got the urge to buy.
And he stayed home - no methadone clinic. No drugs of any kind.
He lives in a rowhouse in Northeast Philadelphia, his father's former business office.
On the morning of March 21, he replied to a text: "I've been up all night in the bathroom. Fell asleep around 7:30. Flu symptoms, cold sweats and insomnia."
That night, he replied to another text.
"I haven't been able to get too far from the bathroom. Taking lots of showers and trying to keep my mind on something other than how sick I am."
That Sunday afternoon - a beautiful day - Hagen emailed: "He seems to being doing well. He has been very quiet and distant (which he is trying to assure me is the withdrawal and not me getting on his last nerve)."
"There's a very somber energy in the air over here, like the way you feel after the funeral of someone who you kind of knew, but not well enough to be devastated. I'd certainly rather be out enjoying the beautiful day and somehow lightening up the mood but I know Pearson needs me here with him, even if it's just to share in the silence. So here I stay."
Crosby, on March 25: "I'm finally starting to eat and sleep again."
On March 26: "I feel like I woke up this morning. I was not fun to be around but I know if I was alone, I would have possibly ran back to the methadone clinic. I know this week took a lot out of Kirsten."
He was now off all prescription drugs.
"All I am fighting now is that constant longing for that unstoppable feeling they give you," he texted on March 27. "Without the back pain, I feel I'm strong enough now to stay off them."
The plan all along, once his body was narcotic-free, was to get a shot once a month of Naltrexone, a drug that blocks the effects of opiates. So even if Crosby were to relapse, the drugs would give him no satisfaction.
But he is still waiting for the shot. His doctors tested his liver function and found certain levels higher than normal. That needs to be investigated, but Oslin said he didn't believe the complication should preclude Crosby from getting the shot.
"If he can stay clean and off the drugs for a year," Oslin said, "that desire and hunger will go away. He's really in a vulnerable place right now."
Each day, Crosby's hanging on.
He has big plans, to start his own security business, get a pilot's license, go back to school.
And this month, he and Kirsten will do something he could never do when tied to daily visits to a methadone clinic. They planned to be on a beach in Puerto Rico.
"He's been in a cave for so long," she said. "I just want to wake him up to the world."