CHICAGO (AP) — A Chicago police officer was unintentionally shot and killed by her partner after they chased a suspect into an apartment and encountered another person with a rifle, officials said.

Krystal Rivera, 36, a four-year veteran of the department, is survived by a 10-year-old daughter.

The partner was the only person who fired a weapon, and the “gunfire unintentionally struck Officer Rivera,” city police said in a statement Friday. An autopsy showed she was shot in the back.

Rivera died at a hospital late Thursday, less than an hour after being shot.

Colleagues had brought her to the hospital in a squad car that crashed and caught on fire due to a malfunction, according to Police Superintendent Larry Snelling. She was then transported in another squad car.

The person who allegedly brandished the rifle was taken into custody, police said. They did not immediately say what charges the person would face.

The shooting occurred just before 10 p.m. on Thursday as Rivera’s tactical unit conducted a stop on someone suspected of having a weapon. A chase ensued that ended in the apartment. Investigators later found three weapons at the scene, police said.

Snelling called Rivera “young, vibrant and a hard worker.”

Her mother told The Chicago Sun-Times that she had dreamed of being a police officer since she was young.

“For me, it’s a privilege,” Rivera told the Sun-Times when she graduated from the academy in 2021. “I come from a family of serving. To help people in need, that’s my calling.”