Chicago (CBS) — Mercy Hospital gunman Juan Lopez began Chicago Fire Department training in March of 2014. Two months later, he was fired, in part, for behavior outlined in a 19-page, internal affairs report.

In it, a fellow female candidate stated Lopez repeatedly hit her with his shoulder, bumping into her frequently and deliberately. The report states she even called him out on his disrespectful conduct, but it continued, sometimes followed by a stare. Signs, Yesenia Maldonado says, of a deeper issue.

“So if we start seeing those patterns happening early in life, know that those don’t change without help,” said Maldonado, the executive director of Between Friends.

Lopez took his own life Monday following a shootout with police after he’d already killed his ex-fiancee Dr. Tamara O’Neal, pharmaceutical resident Dayna Less and Chicago police officer Samuel Jimenez.

A study, conducted by Everytown for Gun Safety, shows 54 percent of mass shootings have a domestic violence component.

“We know one of the most dangerous times for someone in their relationship is actually when they make the decision to leave,” Maldonado said. “When you look at Dr. O’Neal’s case, the relationship was broken off. Many cases happen that way.”

The agency overseeing the state’s domestic violence crisis line said it usually gets 40 calls a day. Monday, after the shooting, the calls doubled.

“Most people who are being harmed in a relationship live in isolation,” Maldonado said. “When they see a story in the media, they see a reflection of themselves … and then they want to reach out and talk to people.”

Maldonado said it’s a courageous first step.

“We also know that it takes people an average of seven times before that they actually make the decision to leave,” she said.

But, leaving isn’t easy. Maldonado said in addition to asking why victims don’t get out of an abusive relationship, we should also ask why abusers abuse. Domestic violence, she said, is a community problem.