Another ex-girlfriend of the gunman in the Dayton, Ohio, massacre says he had a history of “violence towards women” — a tendency that she says should be taken more seriously.

The shooter, Connor Betts, 24, opened fire early Sunday morning in a popular nightlife district, killing at least nine and wounding 14. He was shot dead by police. Betts did not have a criminal record, authorities said.

Lyndsi Doll dated him for less than a year while they were in high school. She told “Today” that when she first met Betts, she remembers “a lot of women coming to me and warning me about his violent tendencies.”

Doll said he was never violent or threatening to her, but fellow students and friends told her about the “rape list” and “hit list” he allegedly made and his threats against women that got him suspended from school.

“I've been very lucky that I never experienced any violence from him,” Doll said, but she said she heard stories of Betts allegedly pushing another woman into a river and threatening, berating and harassing other women. NBC News has not confirmed these reports.

Doll said this pattern of violence worried her. “I confided in other friends, I confided in a few school counselors about some of my fears about how he may harm someone, or harm himself," she said. “I feel like maybe we weren't taken seriously.”

NBC News reached out to Betts' former school for comment but did not immediately hear back.

In the wake of Sunday's rampage, Doll said that “the main issue at hand here is gun violence, and violence towards women.”

Research shows that domestic violence, like substance abuse and a history of violent misdemeanors, is a risk factor for gun violence toward self or others, the Consortium for Risk-Based Firearm Policy found in a 2013 report.

The president of the National Organization for Women, Toni Van Pelt, told NBC News in a statement that, “While we are heartbroken at this latest act of gun violence, it should come as no surprise that the Dayton shooter had a history of alleged physical violence against women, misogynist threats, a fascination with sexual assault and a “hit list” of people he wanted to kill or rape. Mass shooters, like domestic abusers, have a history of using their power to demonstrate their authority,” the statement said in part.

Important first steps toward change “include a meaningful vote on gun violence legislation and reauthorization of the Violence Against Women Act. The Senate simply must act to stop the violence,” the NOW president said.

Another former girlfriend of Betts', Adelia Johnson, 24, told NBC News on Monday that she briefly dated him earlier this year, and she said she too saw warning signs.

He asked her to accompany him as he tried to drop off an anonymous letter to an ex-girlfriend, Johnson said. The letter's message — "You can't escape your past" — worried her, she said. Johnson said she broke up with the gunman shortly thereafter, and told friends he scared her.

Doll said that now, looking back, she wonders what she might have done “to raise awareness that, 'Hey, he's dangerous. He has a history of violence towards women.'”

She said she hopes her community can come together to address gun violence and violence against women. “We need to bring justice to these victims,” she said.