There are no easy answers to preventing massacres such as that carried out by Nikolas Cruz at a Florida high school. Unless that is recognized, it will be impossible to forestall mass killings.

One thing about Cruz does appear clear, however. It is that had his mother, Lynda, not died last year, his homicidal impulses might have been kept in check.

Lynda Cruz died in November. Her son went to live with the parents of a classmate, who told reporters they had no idea he was dangerously disturbed. “We had this monster living under our roof and we didn’t know,” the woman told a reporter.

But Lynda Cruz knew her son had serious problems. He had been a discipline problem at school, to the point he was expelled last year.

Investigators have learned his mother seemed to hold his violent tendencies in check. She made him follow through on therapy and ensured he took his medicine. When he scrawled a swastika and a racial epithet on his book bag, she forced him to erase them. But it appears that after she died, no one suspected the extent of his homicidal hatred.

Will that knowledge help deal with young people like Cruz in the future? We hope so, but it is not a sweeping answer to the problem of mass murders. Sadly, there is none.