That same year, Long enrolled in college. Cal State Northridge enrolls a large number of veterans and has a resource center to serve them. School officials were unable to say if Long had ever used those services.
"Veterans are not 18-year-olds fresh out of high school," said spokesperson Carmen Ramos Chandler. "They have experienced life in a way that so many of our traditional students have not. So we wanted to provide a place where they felt welcomed, warmly."
On Thursday afternoon, half a dozen young men were on laptops, chatting, with a television on in the background. None of them knew Ian David Long from his time at the school.
"It's a hard thing to hear anytime there is a mass shooting. But when it affects young people, it gets personal. We're a university, that's who we are," Chandler said. "People know people who are impacted by this. Our hearts go out to them."
Winnett, Long's former roommate, said he was concerned that Long might have suffered from PTSD, based on conversations he said Long's girlfriends had with him.
Experts caution, however, about tying possible PTSD to acts of violence.
Research on links between mental health disorders associated with military service and violent acts leaves an incomplete picture. Impulsive aggression, like getting into fistfights, has been tied to PTSD. But there was no higher likelihood for premeditated aggression in veterans suffering from PTSD.
"The stigma will only alienate them further," said Dr. Susan Michael with New Directions for Veterans, a nonprofit that provides bridge housing and services to veterans in Southern California.
Long didn't say much about his military experience, Winnett said. Though he was an experienced machine gunner, he didn't come off as particularly interested in weapons.
"He [had] one handgun," Winnett said. "I'm a gun nut. He wasn't."
At some point, Long's college plans began to unravel. University officials said he ended up leaving in 2016 without a degree.
There was a motorcycle accident sometime in 2015 or 2016, Winnett said, that resulted in Long's mom having to care for him.
"Man, I feel bad for her," Winnett said. "She is the nicest person. She doesn't deserve it."
Long moved in with his mother, Colleen Long, in Newbury Park, a middle-class community of ranch-style homes near Thousand Oaks and a short drive up the rocky coast from Los Angeles.
Colleen Long used to frequently post photos of her son in uniform on Facebook. One of the last mentions of his name took place on his birthday on March 27, 2016, when she wrote:
26 years ago my sun was brighten by the birth of my son! Feels like yesterday, Happy Birthday Ian! 😘🍰👏👏
A few months later, she thanks him for a Swiss army knife he appears to have given her as a gift.
But he's scarcely mentioned among her posts from the last two years, which are filled with photos of dogs, hikes and baseball.
Long didn't draw much attention from Ventura County law enforcement in recent years either. There'd been "minor interactions," including for a traffic collision and once when Long was the victim of battery at a local bar, according to officials.
Neighbors described him as quiet until an incident last April that rattled residents.
"I remember hearing a lot of banging noises ... someone pounding," said Tim Tanner. Someone called the cops and officers swarmed in.
"[Long] was just sitting out there talking to an officer," Tanner recalled.
Ventura County Sheriff Geoff Dean described Long during the incident as "somewhat irate, acting a little irrationally."
"They called out our crisis intervention team, our mental health specialists, who met with him, talked to him," Dean said.
But they didn't feel it warranted taking him in on a 5150, the code used for involuntary psychiatric commitment of someone deemed a danger to themselves or others. Long had been cleared.