Paul Anthony Ciancia was a newcomer to Los Angeles -- a 23-year-old Catholic school graduate and son of a popular Fraternal Order of Police member back in New Jersey.
According to a profile emerging of the suspected gunman, he also harbored anti-government views and fears of an ominous New World Order when he walked into Los Angeles International Airport on Friday.
Police say Ciancia pulled an assault rifle out of a bag and opened fire in the airport, killing Transportation Security Administration officer Gerardo Hernandez, 39, and wounding several others, including at least two other agents, in what appeared to be an orchestrated assault on members of the federal agency.
A federal criminal complaint was filed Saturday afternoon charging Ciancia with murder of a federal officer and commission of violence in an international airport, U.S. Attorney Andre Birotte Jr. said.
Investigators unable to interview suspect
Ciancia remained hospitalized Saturday. FBI Special Agent in Charge David Bowdich described him as "unresponsive."
"We are unable to interview him, as of today," Bowdich said.
Asked at a news conference if Ciancia had any known run-ins with TSA officers, Bowdich said, "To this point, we have found none."
Shooter:"Are you TSA?"
Eyewitnesses said Friday's shooter walked from person to person, calmly asking, "Hey, are you TSA?"
"I just shook my head," Leon Saryan, a traveler at the airport, told CNN's Anderson Cooper. "And he kept going."
Ciancia was eventually shot multiple times in the chest and taken into custody as he allegedly continued his eerily calm run through the airport's Terminal 3.
He had enough ammunition to "have literally killed everyone in that terminal," Los Angeles Mayor Eric Garcetti said.
Ex-roommate in L.A. shocked
In the hours after the attack, with the terminal at one of the world's busiest airports still closed, authorities were piecing together a picture of the man in hopes of finding answers.
If they're looking for telltale signs of trouble from before he moved to Los Angeles about a year and a half ago, nothing has emerged, at least publicly.
John Mincey, who said Ciancia was his roommate in a Los Angeles apartment complex until February, said he was "absolutely shocked" by the charges.
"From knowing this guy, I can't believe that he would -- it just doesn't make sense," Mincey told CNN affiliate KABC-TV.
"He would always talk about documentaries he would watch," but Ciancia never talked about "any hatred," Mincey said.
Mincey told KABC he had lunch last week with Ciancia, who said he was going to New Jersey for the holidays and hoped to make amends with his family.
No history of mental illness in New Jersey
Allen Cummings, the police chief in Ciancia's hometown of Pennsville, New Jersey, said Ciancia has no history of violence or recorded mental illness. Family members told police he didn't seem troubled the last time they saw him -- when he visited family for a wedding this summer.
"Obviously, you know, they're upset," Cummings told CNN. "I mean, this is a shock to them. It's a shock to our community."
Ciancia grew up in a quiet, wooded neighborhood just minutes from the Delaware Memorial Bridge, according to The News Journal in Wilmington, Delaware. Houses there are far apart, nestled in the woods at the end of driveways sometimes hundreds of feet long.
He once worked in a popular auto repair shop owned by his father, an associate member of the local Fraternal Order of Police who neighbors say has always been known for how well he takes care of customers there.