The gunman believed to be behind a fatal mass shooting in Thousand Oaks, California, on Wednesday night posted a Facebook message before he opened fire on the crowd at Borderline Bar and Grill, killing 12.

CNN reports that authorities located a Facebook post they believe was  made by Ian David Long shortly before the mass shooting, in which he appears critical of responses to mass shootings in the U.S.

The message read, “I hope people call me insane… (laughing emojis).. wouldn’t that just be a big ball of irony? Yeah.. I’m insane, but the only thing you people do after these shootings is ‘hopes and prayers’.. or ‘keep you in my thoughts’… every time… and wonder why these keep happening…”

Current and former friends of the shooting suspect, who was found dead at the scene from an apparent self-inflicted gunshot wound, told CNN that Long frequented the Borderline Bar and Grill and was part of a community there.

“We would go to Borderline together. He really liked it,” a woman who said she had been friendly with Long for five years told CNN.

“There was a community there. He was a part of that community,” she said. “The whole bar is line dancing. People do choreographed dances for hours, cowboy boots and hats in the middle of the suburbs of Thousand Oaks.”

Thousand Oaks is considered one of the safest cities in the United States, ranked third on a list of the 33 safest cities in America in a recent poll conducted by Niche and published on Business Insider.

Another source who said they used to be friendly with Long told CNN that they had also used to go with Long at the bar where he later staged a massacre, and expressed shock that Long could be capable of such violence.

“I don’t know what the hell happened. He was always happy. I never thought this would ever come from him. We used to go snowboarding all the time. He was a good guy,” the friend said.

A former classmate of Long’s, Todd Stratton, told the news outlet that Long had some anger issues in high school but nothing that appeared particularly concerning.

Defense Department records obtained by CNN show that Long served as a Marine in Afghanistan November 2010 to June 2011. As CrimeOnline previously reported, a neighbor of Long’s speculated on Thursday that the 28-year-old may have been suffering from PTSD.

Thomas Burke, a pastor who reportedly served with Long in Afghanistan, told CNN that he didn’t believe the gunman’s actions should be attributed to mental illness, while acknowledging that trauma Long experienced during what the report described as “intense fighting in Helmand province” during his service there.

“PTSD doesn’t create homicidal ideation,” Burke told CNN. “We train a generation to be as violent as possible, then we expect them to come home and be OK. It’s not mental illness. It’s that we’re doing something to a generation, and we’re not responding to the needs they have.”

Authorities have not yet determined a motive for the attack that killed 11 civilians and a 29-year veteran of the Ventura County Sheriff’s Department, Sgt. Ron Helus.