The teenager who fatally shot a student at a high school in Nashville, Tennessee, livestreamed part of the incident, according to the platform he used, and he was influenced by internet content that authorities described Thursday as “harmful and objectionable.

An AI gun detection system installed in a Nashville, Tennessee high school couldn’t spot the gun a 17-year-old used to fatally shoot another student and himself earlier this week, according to district officials.

Authorities are examining “very concerning online writings and social media posts” connected to the shooter who killed a female student and wounded another student in a Nashville high school cafeteria.