A Texas police department has fired an officer who shot dead a young football player last week and said they will turn over all evidence in the case to a grand jury for possible criminal charges.

Arlington police chief Will Johnson said at a press conference on Tuesday that officer-in-training Brad Miller, 49, had acted irresponsibly and broken protocol at several key moments during an encounter early on Friday morning with 19-year-old Christian Taylor.

He said that when officers arrived and met Taylor, just after 1am, he was inside the glass storefront of a car dealership, and they stood just outside it. Taylor was screaming and had a “bulge in his pocket”, the officers said.

Officers Dale Wiggins and his trainee, Miller, were sent to secure the western perimeter of the auto showroom. Instead, Miller moved ahead, and when he rounded a corner and saw Taylor’s car, which he had crashed into the dealership’s plate glass, he entered through the glass.

Miller should have waited for his partner, Johnson said. He said Miller’s decision to enter alone was “troubling” in several ways: the officers did not know whether Taylor was alone in the dealership, or whether he was armed. Miller and Wiggins should have simply maintained a perimeter and waited.

When Miller entered the dealership, he saw Taylor and pursued him into a back corner of the building. Taylor flung himself against a glass door, with such force that officers on the outside could see the building’s glass exterior shaking.

Meanwhile Wiggins felt he had no choice but to follow his trainee into the building. He told internal affairs investigators he felt “a sense of urgency to rejoin” Miller.

As Wiggins approached the back corner where Miller stood, Taylor turned away from the locked door and approached the officers rapidly, Johnson said. Wiggins unholstered his Taser and heard a pop, which he thought was Miller firing his own Taser. Instead, it was Miller firing his gun.

Wiggins then fired his own Taser, while Miller fired three more bullets.

Johnson said the incident was “a tragic case. Our community is hurting, a family is hurting, our department is hurting, and indeed our nation is hurting.”

Local protesters planned to demonstrate against the shooting on Tuesday night.

Taylor’s father, Adrian, said he felt encouraged by the department’s decision to fire Miller, but was unsatisfied.

“My son is never coming home again,” he said. “So right now I’m not sure there’s anything that could satisfy me.”

Johnson said his department was sharing information with the FBI, although the FBI was not directly involved in the investigation. He said a criminal investigation into Miller’s actions would proceed but could take some weeks.