THOUSAND OAKS, Calif. — The gunman who killed 12 people at a country music bar in Southern California went on social media either during or right before the attack and posted about his mental state and whether people would believe he was sane, law enforcement officials said Friday.

Also, one of the possibilities investigators are looking into is whether gunman Ian David Long believed his former girlfriend would be at the bar, the official said.

Authorities have not determined a motive for Wednesday’s night rampage.

Long, 28, published messages or pictures to Instagram around the same time gunfire erupted inside the Borderline Bar and Grill on Wednesday night, according to two law enforcement officials who spoke on the condition of anonymity.

In the posts, Long wrote that he hoped people would refer to him as “insane” after the shootings, and openly mocked the “thoughts and prayers” that are offered in public statements and on social media after mass shootings, according to one of the officials. The postings have since been scrubbed from Instagram and Facebook, the officials said.

Long, a former Marine Corps machine gunner who served in Afghanistan, opened fire with a .45-caliber handgun during college night at the bar, then apparently killed himself as scores of police officers closed in.

As investigators worked to figure out what set him off, President Donald Trump blamed mental illness, describing the gunman as “a very sick puppy” who had “a lot of problems.”

Investigators have not commented on whether mental illness played a role in the rampage. But a mental health specialist who assessed Long after police were called about his agitated behavior last spring worried he might be suffering from post-traumatic stress disorder.

The incident happened in April, when one of the loud and repeated fights he had with his mother at the home was so bad that a next-door neighbor called police. The mental health specialist concluded there were no grounds to have him involuntarily committed.

At the White House, Trump touted his efforts to fund work on PTSD among veterans. He declined to engage on questions on whether the nation needs stricter gun control laws.

Sheriff’s Sgt. Ron Helus, a 29-year veteran, was gunned down as he entered the bar to confront the shooter. The other 11 victims, most of whom have been identified by relatives or social media posts, are: Sean Adler, 48; Cody Coffman, 22; Blake Dingman, 21; Jake Dunham, 21; Alaina Housley, 18; former Marine Dan Manrique, 33; Justin Meek, 23; Kristina Morisette, 20; Mark Meza Jr., 20; Telemachus Orfanos, 27; and Noel Sparks.

Orfanos survived last year’s massacre in Las Vegas, where a gunman in a high-rise hotel killed 58 people at an outdoor country music festival.

Authorities in Thousand Oaks described an assault of military efficiency. None of those injured was hurt by gunfire, authorities said. Instead, when Long shot, he killed.

“Every Marine is trained in urban warfare and indoor gun fighting,” said Marc Bender, an instructor for emergency responders in Riverside County, Calif. “Every Marine is a marksman.”

Julie Hanson, who lives next door to the ranch-style home that Long shared with his mother, described him as “odd” and “disrespectful” well before he left home a decade ago, got married and enlisted in the Marines. She could often hear him yelling and cursing, but several months ago unusually loud banging and shouting prompted her husband to call authorities.

“I was concerned because I knew he had been in the military,” Tom Hanson said.

Los Angeles Times contributed.