Henry Cox, 19, was arraigned Thursday morning in Rochester City Court on second degree murder charges.
Slater, 49, was gunned down a week ago on Barons Street. He was walking home from a community meeting.
Slater was employed at Action for a Better Community and was on the board of the Rochester Children's Zone.
His murder prompted a zero-tolerance initiative by Rochester police. Officers are working 12 hour shifts and walking the beat to curb violence and prevent any more homicides.
Calling hours for Slater are to be held Thursday. His funeral is set for Friday.