Police say someone threw black paint on the huge mural, splattering Rizzo's left eye and much of his face. Authorities say they are investigating, but no arrests were immediately announced.
Rizzo was police commissioner before serving two terms as mayor from 1972 to 1980. He died in 1991. He earned legions of supporters and detractors for his tough law-and-order stances.
His son, former City Councilman Frank Rizzo Jr., tells the Philadelphia Daily News his father was knocked down a few times in his life and that the mural will be fixed back up.
