BALTIMORE >> Baltimore police officers responding to the sound of gunshots near an apartment building fatally shot a man who fired at them with an “AR-15-style” gun, authorities said early Friday.

No officers were wounded, police spokesman T.J. Smith said, adding it wasn’t immediately clear why the man had begun shooting.

Four plainclothes officers riding in an unmarked car heard gunfire coming from the building on the city’s west side Thursday night, Smith said. The officers drove toward the sound and when they arrived, they saw a man shooting an “AR-15-style” gun, according to Smith.

The man started firing toward the officers, and two returned fire, Smith said. The suspect was shot at least once and retreated to the apartment building, according to the spokesman.

Officers, who Smith said initially thought there was more than one suspect involved, surrounded the building and searched the scene.

He said authorities found the gun in a tree line behind the apartment complex and the suspect inside with at least one bullet wound to his upper body. The man, who wasn’t immediately identified, was taken to a hospital, where he was pronounced dead.

Smith said an investigation was opening but he didn’t immediate identify the officers, the man or the races of those involved. He said the officers who fired their weapons were being place on routine administrative duties as is customary.

“We don’t have a victim … No one has come forward and said, ‘Hey, I was being shot at,’” he said.

The idea that the man was trying to lure officers to the scene with the gunfire is a “theory” police are looking into, Smith said.

While the officers were in plainclothes, they were also wearing outer vests that were marked “police” on the front and back, he said.