NEW YORK (CBSNewYork) — The man who police said barricaded himself inside a Staten Island home and shot a firefighter Friday was being investigated in connection with several homicides, police sources told CBS2.

Garland Tyree, 38, was killed when he allegedly came out shooting at officers just before noon Friday following a six-hour standoff, at his girlfriend’s home in the Mariners Harbor section of Staten Island.

A police source told CBS2’s Jessica Schneider that Tyree was being investigated in several homicides in the city.

Tyree was a self-proclaimed gang member, and sources said they were concerned that members of the gang – a subset of the Bloods – could strike back after his death, Schneider reported.

A U.S. Marshals regional task force had come to arrest Tyree around 5:45 a.m. Friday on federal parole violation charges.

Police sources told CBS2 Tyree’s parole violation involved a recent trip he made to the Bahamas. Conditions of Tyree’s federal parole forbade him from traveling without permission – which he did not receive – and forbade him from traveling outside the country at all, sources said.

As officers arrived to serve the warrant, they were “confronted with a smoke-filled situation” inside the basement apartment, which prompted them to call firefighters, Police Commissioner Bill Bratton said.

When firefighters responded to the scene, Tyree opened fire, striking 53-year-old FDNY Lt. James Hayes.

For close to six hours, there was dialogue between negotiators, the suspect, and his loved ones.

Police said Tyree was armed with an assault rifle and was believed to be the only person inside the home. Authorities said they later determined that the smoke was caused by a commercial-grade smoke bomb.

But police said just before noon, six hours after the standoff began, Tyree exited the home shooting and the standoff ended with his death.

In a video posted to YouTube a year ago, Tyree talks about gang life – detailed in a book he wrote. Early Friday, he posted three words to his Facebook page: “Today I die.”

Police said Tyree had 18 prior arrests.

“He has been in and out of jail, he has been arrested for numerous crimes before,” Chief of Detectives Robert Boyce said. “He has been out of jail on probation since last summer, July of last summer. He violated those conditions of his probation, that’s why we’re here today.”

Boyce said Tyree had previously been convicted of weapons, drug and assault charges.

He has been on probation since last summer, and was arrested for murder, but convicted on a lesser charge, in the early 1990s, officials said.