Chicago Police Department officer Aréanah Preston, 24, was walking home from work on Saturday when she was shot and killed.
Police arrested Joseph Brooks and Trevell Breeland, both 19, as well as Jakwon Buchanan, 18, and a 16-year-old boy in connection with the shooting, CBS News reports.
All four have been charged with first-degree murder and armed robbery. The 16-year-old will be tried as an adult, according to CBS Chicago. They have also been charged with burglary, motor vehicle theft, and other offenses related to incidents on Friday and earlier on Saturday.
Police said Ms Preston was shot around 1:40am during a robbery spree. The suspects allegedly spotted Ms Preston walking home after her shift while driving around in a sedan. Residential surveillance video viewed by police alleges that the suspects ran up to Ms Preston while she was outside her home and fired at her. One of the suspects allegedly grabbed Ms Preston's gun before they fled in the car.
An initial emergency call around 1:42am was made to police, but due to delays police did not immediately respond to the call. A second 911 alert was sent from Ms Preston's Apple Watch approximately 20 minutes later.
The 16-year-old allegedly bragged about the shooting to a friend, who then reported it to the police, according to CBS Chicago. The friend then called the teen back, but with detectives listening in on the call.
"During this phone call defendant, [the suspect] made additional admissions to the robbery and the shooting - including details that had not been released," Assistant State's Attorney Anne Rodgers McCord said.
Judge David Kelly ordered the four suspects to be held without bail during a hearing on Wednesday, citing a "mountain of evidence" collected by prosecutors.
The city's mayor, Lori Lightfoot, issued a statement following the announcement that Ms Preston's alleged killers had been apprehended, calling the incident a "heinous murder."
Ms Preston was only three years into her job with the department when she was killed.