"We don't feel safe. Faculty don't feel safe... if parents knew how unsafe the inside of the school is, they would be upset," one teacher told KPRC 2.

William Kenneth Howard's handgun was unsecured and unlicensed when it fell out of his knapsack in a hallway at Cody High School, according to authorities.

Criminal investigations of parents as well as schools are rare, experts say. But they appear to be gaining traction as communities demand accountability and new ways to prevent the violence.

"The vast majority do not go into the education field to play the role of a police officer," says Kenneth Trump, president of the National School Safety and Security Services.