DENVER — A 21-year-old man was arrested for investigation of first-degree murder, after a veteran Denver policewoman who was raising her 12-year-old daughter alone was shot and killed during a free jazz festival, police said Monday.

Suspect Rollen Oliver was taken into custody late Sunday after witnesses gave a description of the gunman. Police also recovered a gun and said they believe Oliver was the only person involved in the attack.

Police Chief Robert White said investigators were not sure if Officer Celena Hollis was the target of the shooting when she answered a call about a disturbance in the park.

“There was a tragic event last night and a beautiful young, single mother and a valuable member of the Denver Police Department lost her life,” Public Safety Manager Alex Martinez said. Authorities said they did not know the cause of the disturbance.

Oliver appeared in court Monday and was ordered held without bond. District attorney’s spokeswoman Lynn Kimbrough said a decision on charges was not expected until later this week.

Oliver was escorted into the courtroom by six deputies, all wearing black and blue bands of mourning over their badges.