The suspected gunman who killed 12 people at a country music bar in Southern California went on social media during the attack to post about his mental state and whether people would believe he was sane, a law enforcement official said on Friday. Investigators are also looking into whether suspect Ian David Long believed his former girlfriend would be at the bar, the official said. Authorities have not determined a motive for Wednesday night’s rampage at the Borderline Bar & Grill. The official – who was briefed on the investigation but not authorised to discuss it so spoke on condition of anonymity – would not say what the 28-year-old former marine posted on Facebook and Instagram. Long, a former machine-gunner who served in Afghanistan, opened fire with a handgun during college night at the bar, then apparently killed himself as scores of police officers closed in. As investigators tried to work 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 last spring worried he might be suffering from post-traumatic stress disorder. Every Marine is trained in urban warfare and indoor gun fighting. Every Marine is a marksman Marc Bender, an instructor At the White House, Trump touted his efforts to fund work on PTSD among veterans. He declined to engage on questions on whether the country needs stricter gun control laws. The dead in the shooting rampage included sheriff’s sergeant Ron Helus, a 29-year veteran gunned down as he entered the bar, and Telemachus Orfanos, 27, who survived last year’s massacre in Las Vegas, where a gunman in a high-rise hotel opened 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, California. “Every Marine is a marksman.” Julie Hanson, who lives next door to the Longs, 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 swearing, 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. About 18 months ago, Don and Effie MacLeod heard “an awful argument” and what he believes was a gunshot from the Longs’ property. Don MacLeod said he did not call police but avoided Ian Long. “I told my wife, ‘Just be polite to him. If he talks, just acknowledge him, don’t go into conversation with him’,” Don MacLeod said. Long had made others feel uncomfortable for years. Dominique Colell, who coached athletics for girls at the senior school where Long was a sprinter, remembers an angry young man who could be verbally and physically combative. Colell said Long once used his fingers to mimic shooting her in the back of the head as she talked to another student. Another time, he grabbed her rear and mid-section after she refused to return his phone call. “I literally feared for myself around him,” Colell said. “He was the only athlete that I was scared of.” Colell said she wanted to kick Long off the team but the boy’s coach urged her to reconsider because that could compromise his goal of joining the marines. She relented when, at the next track meet, Long apologised in front of several coaches and administrators.