KANSAS CITY, Mo. (AP) — A former Missouri police officer has pleaded guilty to violating the constitutional rights of a minor by deliberately dropping the restrained teenager face-first onto the ground.

Federal prosecutors in Kansas City on Friday announced that former Independence officer Timothy Runnels admitted his role in a Sept. 14, 2014, confrontation with 17-year-old Bryce Masters.

Prosecutors say Runnels used a stun gun on Masters during a traffic stop even though the youth was not a threat. Masters went into cardiac arrest and was placed in a medically induced coma and treated for lack of oxygen to the brain.

He was released from the hospital a week later.

Runnels was indicted in March on four federal charges accusing him of using excessive force and hindering the police department’s investigation of the incident.