Ian David Long showed troubling signs long before his murderous rampage.

The high-school track coach of the Thousand Oaks, Calif., mass shooter told BS Los Angeles on Thursday he groped her during his senior year of high school. Dominique Colell recalls the attack taking place during Long’s senior year at Newbury Park (Calif.) High School during a track practice in which he exploded over a misplaced cell phone.

“He attacked me'” Colell said. “He attacked his high school track coach. Who does that?

“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.’ ”

Colell said she declined to press charges against Long after the school and other coaches advised her to accept his apology. She now regrets her decision not to report him to authorities. Had she reported the attack it would have jeopardized Long’s future in the Marine Corps.

“I should have reported it then,” Colell said.

Long, 28, killed 12 people and wounded several others with gunfire Wednesday night at Borderline Bar & Grill in Thousand Oaks before apparently killing himself.

Thumbnail photo via Ringo Chiu/ZUMA Wire/USA TODAY NETWORK