Law enforcement officials seeking a motive for a shooting at Nashville’s Antioch High School on Wednesday morning are examining alarming social media posts and writings tied to a teenager police say shot and killed a 16-year-old girl.

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.