A woman who coached Thousand Oaks shooter Ian David Long in high school has alleged that he assaulted her during that time, and she says signs of him being "mentally disturbed" went unreported.

12 people died, and more than 15 others were injured after Long walked into the Borderline Bar & Grill late Wednesday night (Nov. 7), deployed a smoke device and began firing into the crowd of people who were there for college country night. Long also died at the scene, and investigators believe he took his own life. They have not yet established a motive for the crime.

Dominique Colell coached Long in track at Newbury Park High School, and she tells KCAL in Los Angeles that the alleged assault happened during practice. Someone had found a phone, and as Colell was trying to find out whose phone it was, she says, “Ian came up and started screaming at me that was his phone. He just started grabbing me. He groped my stomach. He groped my butt. I pushed him off me and said after that, ‘You’re off the team.’ ”

Remember the Borderline Bar and Grill Shooting Victims:

Colell says other coaches and the school encouraged her to accept an apology from Long instead of reporting the incident to authorities so it wouldn't have a negative impact on him joining the Marines. She regrets that decision now.

A neighbor described Long as having PTSD, telling ABC News, "I don't know what he was doing with a gun." But Colell says the signs were already there in high school that something was wrong, before he joined the Marines and served as a machine gunner in Afghanistan.

“There are hundreds of thousands of people with PTSD,” she states. “They don’t go around shooting people. This kid was mentally disturbed in high school. There were signs and the administration knew it.”

Long had been living with his mother in recent years, and neighbors have reported loud fights between the two. Authorities responded to the house after a disturbance in April, and they found Long "somewhat irate and acting irrationally." A mental health specialist met with him and concluded that he couldn't be committed for involuntary psychiatric observation at that time.

Department of Veterans Affairs spokesperson Curt Cashour tells USA Today that Long was “not enrolled in VA health care at any time."

Barbara Olasov Rothbaum, the director of the Trauma and Anxiety Recovery Program at Emory University School of Medicine, tells USA Today that people should not rush to blame PTSD or mental illness for Long's shooting spree.

“I get upset when people get scared of veterans with PTSD because they think they are going to be violent, and they’re not,” she says. “There is already so much stigma involved in PTSD in general — and certainly in veterans and military service members — that anything else that adds to the stigma would do them a disservice."

Friends of Long's who spoke to CNN painted a very different picture of his character, saying that he was a regular at the Borderline, where "he was a part of that community." Describing him as "sweet," a "good guy" and "always happy," they expressed shock at his crime.

Long's former roommate, Blake Winnett, echoed those thoughts in an interview with the Today show, saying, "I just want to set things straight — he wasn't a bad person."

"From what I know, he was a great person. He was just quiet, secluded," Winnett described Long during the more than two years they lived together. Long was out of the Marines and attending college during that time.

"I want to understand this. I like the guy. I don't know why he would do something like this," Winnett adds. He thinks the "government messed him up," saying, "Well obviously, he's got an illness. And as you guys refer to it as PTSD. The government should be fixing that. ... It's his problem, but it's not his fault."

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