Once again our children have paid with their lives to teach us a lesson about school violence. It is that banning so-called “assault rifles” or even semi-automatic pistols will not stop them.

It is that people kill people, and unless we learn more about what triggers homicidal behavior, the deaths will continue.

A secondary lesson to the killings in Santa Fe, Texas, is that we are at a loss to find answers to the first question.

Dimitrios Pagourtzis, 17, went to his high school in Santa Fe with murder on his mind Friday. Hidden underneath the trench coat he often wore were his father’s shotgun and .38-caliber revolver.

By the time he stopped shooting, 10 people, most students, were dead. Several others were injured.

Authorities said there were no red flags indicating Pagourtzis was a threat. He had never been in trouble with the law or at school. He seemed to be a reasonably good student, involved in athletics and other extracurricular activities. He was active in his church.

He liked video games — but what youngster doesn’t? A girl in the school had rejected his advances recently, but, again, that happens all the time.

His family released a statement that “what we have learned from media reports seems incompatible with the boy we love.”

If there is a clue, it is among his fellow students. Some told reporters Pagourtzis may have had certain targets. What do his peers know about his motivation in wanting to kill specific people?

Everything it is possible to know about Pagourtzis needs to be uncovered. The fact he survived his spree will help.

The only way we can curb violence by and against our children is to discover more about why some decide to kill. The longer that takes us, the more of our children will be murdered.