A POLICE officer and mum-of-one was shot and killed unintentionally by a colleague while on duty.

Krystal Rivera, 36, who worked for the Chicago Police Department in Illinois, lost her life during a confrontation between police and armed suspects.

The tragedy unfolded when Rivera and other officers were patrolling the city’s East Chatham neighbourhood on Thursday, as reported by NBC Chicago.

They decided to investigate a suspect believed to be armed at 9.50pm.

The suspect fled on foot into a nearby apartment as cops ran behind, according to Chicago Police Department Supt. Larry Snelling.

When police entered the apartment, another person pointed a rifle at them.

An officer discharged his weapon during the confrontation leading Rivera to be shot, Snelling said.

While on the way to the hospital, the police vehicle Rivera was in reportedly caught fire, necessitating her transfer to another car, according to Snelling.

She was pronounced dead at the hospital, police said.

Another officer suffered a wrist injury, requiring hospitalization, according to Fox 32 Chicago.

At 3am, dozens of police officers and firefighters walked in a solemn procession from the hospital to the Cook County Medical Examiner’s Office to pay their respects.

The Chicago Police Department described Rivera as a “brave and caring officer who dedicated her career to assisting others and safeguarding our city.”

Snelling revealed Rivera was a four-year veteran and the mother of a young daughter: “She was a mom, and there’s nothing like walking into a room and having to deliver this type of message to her mother and her very young daughter and the rest of her family.”

He added: “She was a hero, and she lost her life tragically doing the job that she loved.

“That was one of the things that her mother said, she loved her job, and the way that she worked.”

In an Instagram post, the Chicago Fire Department posted a picture of the tragic officer, saying she “made the ultimate sacrifice in service” to the city.

According to Snelling, two people inside the apartment fled the apartment but were taken into custody soon after.

He added that “several individuals” are in custody, as three weapons were recovered from the scene.

Police and the Chicago Office of Police Accountability, which assesses incidents that involve officers firing weapons, are conducting an investigation.

Speaking about Rivera, Snelling said: “She had already processed two other guns working that day.

“She was a working police officer trying to keep the street safe. And she did great work.

“And if you talk to anyone on her team, they would tell you how great of a worker she was.

“This is the risk that our officers take every single day.”

He added that “this happens way too often”:

“An officer, a young officer, 36-years-old and four years on the job. Who was working hard… these officers are out here driving down crime while putting their lives at risk.

“I want everyone to keep this officer’s family in your prayers and understand the risk that she took every single day when she came out to do her job.”

Police are reportedly issuing a search warrant for the apartment, and a forensic investigation is said to be underway in the apartment