The man accused of shooting a Denver police officer to death at a jazz concert claimed to be a member of the Park Hill Bloods street gang when he was booked into jail, according to documents obtained by The Denver Post.

Rollin Oliver, 21, is accused of shooting officer Celena Hollis in the head as she attempted to help break up a fight between two groups of people.

Hollis, 32 and a single mother with a 12-year-old daughter, was working off-duty as part of a security detail at a City Park Jazz concert on Sunday when she was shot. She was in uniform.

At a press briefing on Monday, Police Chief Robert White said investigators didn't know if Oliver was a gang member. He did acknowledge that investigating officers had been told that the confrontation that led to the shooting was sparked by gang tensions.

On Tuesday, White said he was given conflicting information after the arrest, and had heard that Oliver had both claimed and denied gang affiliation.

"I am not going to give out information unless I am sure it is right," he said.

Oliver was being held Tuesday on suspicion of first-degree murder. He has not been formally charged.