CHICAGO — Cook County prosecutors say they will appeal a judge’s decision not to give a life sentence to a man convicted as a teenager in the 1995 shooting deaths of two 13-year-old girls.

Eric Anderson was 15 when he was convicted. The son of a Chicago police officer, he opened fire at a gang rival but fatally shot the girls outside an elementary school.

Anderson’s sentence was vacated when the U.S. Supreme Court ruled in 2012 that giving sentences of that length to juveniles was unconstitutional.

The Chicago Tribune reports ( Judge Arthur Hill Jr. cited that ruling Tuesday when he said he could sentence Anderson to between 20 and 60 years in prison. He also asked prosecutors and defense attorneys to submit legal filings on whether Anderson qualified for “good time credit.”

Information from: Chicago Tribune,