More details are coming out regarding Connor Sturgeon, a day after he carried out a mass shooting in Kentucky. According to a report, Sturgeon was a star athlete and played football in school. He had a history of suffering serious injuries while playing the sport according to one of his ex-classmates, who talked to Daily Beast.

As a result of multiple concussions, Sturgeon was out of football for most of the year during 8th grade. “Then he had a couple more in high school. I’m not saying it’s the cause but I always think back to that. There were times I’d wonder, will this catch up with him? But never in this way. He’s the last person I’d expect would do this,” the ex-mate said.

Since he wanted to continue his athletic career, he was forced to wear a helmet in games. He was immensely supported in high school to pursue a sports career. He played on the Varsity basketball team and ran track. Despite the support, Sturgeon suffered from low self-esteem throughout his young life.

In an essay written by him from his college days, that has resurfaced in the wake of the recent shooting, Sturgeon wrote that he hoped to better himself when he grew up. “Making friends has never been especially easy, so I have more experience than most in operating alone,” he wrote in the essay. He also added that he would often find himself battling “against myself.”

Police told NBC News Sturgeon may have suffered from mental illness.