Lopez had no criminal record, but he’d shown warning signs of instability and misogyny in the past. Nearly five years ago, he threatened violence against his classmates at the Chicago Fire Academy, according to the Tribune.

“He was accused of aggressive and improper conduct toward females at the academy,” Chicago Fire Department spokesman Larry Langford said. “He was disciplined and terminated.”

Domestic violence is far more prevalent in our society than mass shootings. The majority of domestic abusers don’t go on to commit mass shootings. But researchers have identified some behavior ― strangling, stalking and death threats ― as key warning signs that an abuser is likely to kill in the future.

Often, as was the case in Chicago, the victims are their partners, as well as anyone else who happens to be around at the time.

Clarification: Language in this piece describing Dayna Less' position at the hospital has been amended to specify that she was a pharmacy resident, not a pharmacy assistant.