The Denver police department arrested a man on murder charges in the shooting death of a policewoman, Celena Hollis, at City Park during a free jazz concert Sunday night.

The suspect, Rollen Oliver, was arrested after being identified by residents attending the City Park concert, the Associated Press reported. He was charged with first-degree murder.

Hollis, 32, a single mother, was shot in the head while trying to break up a fight that broke out after a jazz band completed its set. Three shots rang out around 8 p.m., scattering people from the park, according to several reports. Hollis died at a local hospital, the Denver Post reported.

The Denver police department lost one of our finest tonight, a post on its Twitter account said. Please keep the officer & her family in your prayers. Thank you for your kind thoughts and support.

Hollis had been on the force seven years, since moving from Detroit in 2005. Denver Police Chief Robert White announced an arrest during a news conference Monday morning.

City Park was closed Monday while police searched the area for evidence in the shooting, the AP reported.

The Denver Police Department urged anyone with information on the shooting to contact its tip line at 720-913-STOP.

The incident led City Park to become a trending topic on Twitter in the Denver area.

Our thoughts are with the family and friends of the Denver Police Officer killed in last night's City Park shooting, said the Twitter account for Lala's Wine Bar.

My thoughts & prayers go out to family of the officer killed in CityPark last night, posted U.S. Rep. Diana DeGette (D-Colo.) A tragic loss for Denver's finest.

Denver Deputy Mayor Michael Hancock said the shooting should not tarnish the city's safe reputation.

We will not surrender this city to anyone, Hancock told the Denver Post.

Hancock said he knew Hollis on a personal level, according to KDVR.

She was a very dedicated officer and a tremendous leader, Hancock said. This is a great loss for our city and a senseless crime. This was a single mother with a beautiful child.

We will put our arms around this child and this family and make sure they know there's a city who absolutely loves them.

The free jazz concert paid homage to jazz bassist and Denver Symphony Orchestra member Charlie Burrell.