Transit authorities say a trolley operator was on his cell phone prior to last year's collision with another train in Boston that sent 16 people to the hospital.

The Boston Globe reports 42-year-old Leroy Mattison, of Malden, told investigators he was trying to delete a post he had made on Reddit at the time of the crash Dec. 29. Authorities say he also had a loaded .40-caliber handgun in a backpack on the trolley.

Court records show transit police are seeking criminal charges against Mattison that include negligence, witness intimidation and using a mobile phone while operating a public transport vehicle.

The Massachusetts Bay Transportation Authority said Monday Mattison has been fired following the police report. Mattison has declined to comment.