Santa Cruz police have arrested a 16-year-old suspected gang member in the fatal shooting of a 15-year-old Watsonville boy visiting an apartment in Santa Cruz on Monday evening, police said Tuesday.

The teen suspect is a Santa Cruz resident and known member of the Norteno criminal street gang, but his gang affiliation was not a motive in the shooting, Santa Cruz police Deputy Chief Steve Clark said.

The juvenile was arrested and booked into Santa Cruz County Juvenile Hall on suspicion of involuntary manslaughter, Clark said.

The 15-year-old boy was mortally wounded inside a bedroom of an apartment at 238 Center St. in Santa Cruz on Monday, Clark said.

Officers responded to reports of a victim suffering from a gunshot wound at the address at around 6:45 p.m., according to police.

Police immediately attempted life-saving measures, including putting pressure on the wound and CPR, in an unsuccessful attempt to save the boy, Clark said.

A handgun that officers believed was used in the shooting was found outside the home and had been reported stolen last month.

The firearm was taken during a burglary of a car parked in the driveway of a home, police said.

Several people were inside the apartment at the time of the shooting, according to police.

Officers took all of the occupants to the Police Department for questioning on Monday night.

They were still questioning witnesses and gathering evidence Tuesday after completing their work at the crime scene early Tuesday morning, Clark said.