A convicted felon was charged Wednesday in the deadly shooting of Chicago Police officer Enrique Martinez that erupted during a traffic stop earlier this week in the South Side Chatham neighborhood and also claimed the life of the vehicle's driver.Darion McMillian, 23, from Harvey, faces felony charges of first-degree murder in the killings Monday night in the 8000 block of South Ingleside Avenue, Police Supt. Larry Snelling told reporters at Public Safety Headquarters. McMillian used a handgun that was equipped with an extended magazine and was modified to fire automatically, Snelling said.“On Monday night, our department and our city lost a hero when officer Enrique Martinez was shot and killed protecting the city of Chicago," Snelling said. "Today is the first step in bringing his killer to justice.”McMillian also faces felony counts of attempted murder of a police officer, burglary, possession of a machine gun and possession of a gun as a felon, Snelling said. Chicago Police Officer Enrique Martinez was shot and killed during a traffic stop in the Chatham neighborhood on Monday, Nov. 4, 2024. Mayor Brandon Johnson said Martinez had “courageously protected this city.”Chicago Police Department Mayor Brandon Johnson and Cook County State's Attorney Kim Foxx joined Snelling to announce the charges. Foxx said McMillian is expected to appear at an initial court hearing Thursday at the Leighton Criminal Courthouse.Chief of Detectives Antoinette Ursitti said a second person taken into custody was released after investigators determined he "was not involved in the murder of our officer.”Ursitti said Martinez and his partner tried to stop the vehicle about 8 p.m. Monday and were assisted by other officers in the area. As Martinez and his partner spoke to the driver, they noticed McMillian reaching for a bag and ordered him to stop. That's when McMillian opened fire, striking Martinez and the driver multiple times. Related Suspect released in slaying of Chicago police Officer Enrique Martinez, another remains in custody McMillian then pushed the driver out of the vehicle and tried to drive in reverse as an officer attempted to pull him out, Ursitti said. The officer was dragged from the vehicle, and his gun fired once into the ground.After the vehicle crashed into a parked car, McMillian ran into an apartment with a woman inside, Ursitti said. He used a knife to cut off an electronic monitoring bracelet and fled to the 8000 block of South Maryland Avenue, where he was taken into custody.Ursitti said she hopes securing the charges "brings a small measure of comfort knowing the person responsible for his murder will face justice.”Johnson said Martinez "saved lives, even though he knew it could cost him his own.""This exemplifies what our police officers do every single day," Johnson added. "They know the sacrifices, as well as the risks, of their profession, but yet still they work every day to protect us.” Chicago police work the scene where Officer Enrique Martinez was shot and killed in the 8000 block of South Ingleside Avenue in the Chatham neighborhood, Monday, Nov. 4, 2024.Tyler Pasciak LaRiviere/Sun-Times Alleged shooter was already facing chargesMcMillian had been placed on electronic monitoring in Will County after a recent arrest in Chicago.The Will County sheriff’s office issued a warrant for McMillian’s arrest last month, and he was charged with a felony for allegedly trying to foil a drug test, according to court records and Ursitti. At the time, McMillian was already facing felony cannabis charges.Chicago police arrested him Oct. 11 on the warrant, court records show. After he was released on electronic monitoring in the new case, Will County prosecutors sought to have him detained pending trial on the cannabis charges. That case was continued on Oct. 28.McMillian previously pleaded guilty to a felony charge of shooting into a vehicle in May 2021, court records show.While he was being held in jail in that case, he was hit with additional felony charges stemming from a group attack on another inmate. He pleaded guilty to a battery charge that was reduced from a felony to a misdemeanor on the same day as his other plea deal.McMillian was sentenced to four years in jail in the shooting case, as well as mandatory supervised release, records show. He was only given fines and forced to pay court costs in the other case.Snelling insisted that McMillian "should not have been on our streets with a fully automatic weapon."“We all need to be outraged at the violent offenders who are creating endless cycles of trauma in our communities," he said. "We need to be outraged at the proliferation of guns that are killing our residents, our children and our first responders."He invoked other young officers who have been killed in the line of duty in recent years: Luis Huesca, Aréanah Preston, Andres Vasquez Lasso and Ella French.Foxx noted she had appeared at a similar news conference just last week to discuss officers who had been fired upon but weren't harmed. Like Snelling, she blamed Chicago's intractable violence on what she described as an "over-proliferation of guns."“We need reasonable, commonsense gun legislation nationally, with an impact here in Cook County," she said.