(Photo: Carlos Osorio - AP)

A gunman opened fire inside a Detroit police precinct on Sunday, wounding four officers including a commander before police shot and killed him, authorities said.

Sgt. Todd Eby told the Detroit Free Press that he was sitting at his desk at the precinct when the gunman walked in around 4:20 p.m. with a pistol grip shotgun and opened fire. He said officers shot back at the gunman, killing him.

Police Chief Ralph Godbee said the gunman has been identified but it was "too early to characterize" him Sunday evening while the investigation was ongoing.

The chief said along with the commander, two sergeants and an officer were wounded, but none appeared to have life threatening injuries.

The commander, who was shot in the back, appeared to be the most seriously wounded. Godbee said he underwent surgery Sunday evening and his prognosis was "very good." A sergeant and an officer who each suffered graze gunshot wounds to the head were both talking and alert, Godbee said.

A female sergeant also was treated and released after her bullet-resistant vest deflected a bullet to the chest, Godbee said.

Police also did not immediately release names of the wounded officers, saying families had not been notified in all cases.

While the department was "very sobered" by the shootings, Godbee said he was "just very relieved that it appears all of our officers are going to be OK."

The precinct, a one-story brick building, is located along a main street in what is predominantly the business district of the neighborhood on the northwest side of the city. Like other precincts in the city, there are no metal detectors at the entrance of the building and visitors are permitted to come in and talk with police face-to-face.

After the shooting, city and state police squad cars converged on the scene, and an ambulance was seen taking away at least one victim.