Chicago Police Superintendent David Brown tweeted Friday that an individual was arrested on a separate warrant in Pennsylvania by the FBI and is currently being held on a $2 million murder warrant.
Brown said Chicago police are seeking his extradition to the city.
Brown did not immediately identify the individual.
Devin Barron, 20, of Lynwood was charged with one count of first-degree murder, one count of unlawful use of a weapon on a person with a loaded firearm, both felonies, as well as one misdemeanor charge of possession of cannabis more than 10-30 grams, one count of being a fugitive from justice with an out of state warrant, and two counts of issuance of warrant earlier this week in connection with Williams' death.
Barron was taken into custody by the Great Lakes Regional Fugitive Task Force Saturday morning around 10 a.m. in Lansing, Ill. He was due in bond court in Chicago Monday.
Dwain Johnson, 18, and a 15-year-old boy who has not been identified by name have also been charged in the shooting.
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Williams, a beloved retired CFD lieutenant, was walking out of a popcorn shop in Morgan Park at 117th Street and Western Avenue on Dec. 3. Surveillance video captured the shooting exchange with Williams and the group trying to approach him. Williams was hit and later died.
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CPD said carjackings are up dramatically this year in the city. The superintendent added that his officers have taken some of the people responsible for these crimes off the streets.
"We've had an extraordinary spike but we have made some arrests," Brown said. "We need to make many more arrests. We're not satisfied and we're not going to stop pursuing these suspects until they're all captured."
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Family, friends and a community said a final goodbye to Lt. Dwain Williams last weekend.
Williams, 65, spent 28 years with the Chicago Fire Department and later worked at OEMC specializing in coordinating the city's surveillance cameras.