A 29-year-old Chicago police officer was killed and another was wounded in an exchange of gunfire during a traffic stop, officials said Sunday.

Ella French was the first Chicago police officer fatally shot in the line of duty since 2018. She had been with CPD since April 16, 2018.

Speaking to reporters about the shooting, Mayor Lori Lightfoot urged Chicagoans to end what she called “the constant strife” over the roles of police.

“The police are not our enemies,” she said during a news conference Sunday. “We must come together. … We have a common enemy: It’s the guns and the gangs.”

Officers had stopped a vehicle with two men and a woman inside just after 9 p.m. in the 6300 block of South Bell Avenue in the West Englewood neighborhood. A male passenger then opened fire, Chicago Police Superintendent David Brown said during the same news conference.

Officers returned fire, striking the passenger who appeared to fire at them, Brown said. He did not release the condition of that man. All three are in custody, but no charges have been filed, he said.

When asked about the condition of the injured officer, Brown responded, “Critical. We need your prayers.”

The superintendent said it was too soon to say why the vehicle was stopped and what might have happened just before the shooting began. He said available evidence included police body camera footage. A gun was also recovered at the scene.

A crowd of officers gathered outside the hospital’s ambulance entrance overnight, some hugging and praying.

Speaking earlier Sunday, Lightfoot said the officer who died “was very young on the job, but incredibly enthusiastic to do the work.”

The last Chicago officer shot to death in the line of duty was 28-year-old Samuel Jimenez, who was killed after responding to a shooting at a hospital on Nov. 19, 2018.

Two officers, Conrad Gary and Eduardo Marmolejo, died when they were struck by a train while pursuing a suspect on Dec. 17, 2018. The department also considers the COVID-19 deaths of four officers last year line-of-duty deaths.

Brown said 38 officers have been “shot at or shot” this year, and 11 have been struck. Last year, 79 officers were shot at or shot, he said.