Chicago police say they continue to question people, but have not charged anyone in the shooting death of Ofc. Clifton Lewis.
"I'd love to tell you we've got it, but we don't right now," McCarthy said at Area 5 Headquarters.
McCarthy said the case is ongoing and that several people are being questioned, as has been the case since last Friday. He declined to comment specifically on the three people a source told NBC Chicago were being questioned Thursday.
A police source said three people were picked up Wednesday night, adding that one of them is cooperating with police and providing "lots of information."
The news came as family, friends, colleagues and city officials gathered to say goodbye to the fallen officer, who was gunned down as he worked his part time job at a small grocery store a week ago.
The 6 foot, 5 inch tall Lewis had eight years of service with the Chicago Police Department. He'd earned 81 commendations during his time with the force.
Clifton was one of two officers killed in 2011. Officer Hester Scott was found beaten to death in November, her body found in a sewer trap behind her Gresham home. Scott's grandson, Keshawn Perkins, was charged with first-degree murder.