Authorities say they've charged a Syracuse teenager with the unprovoked beating of a 70-year-old man outside a convenience store, an attack that left the victim in serious condition.

Police Chief Frank Fowler says Monday that 18-year-old Romeo Williams has been charged with second-degree assault after Saturday morning's beating of Jim Gifford as he walked across the parking lot outside a 7-Eleven store.

Fowler says Williams hit Gifford in the face, knocking him unconscious. Police say Williams then entered the store and celebrated by taking off his hat and holding it up in the air and smiling before going back outside to beat and kick Gifford.

Fowler says four men with Williams eventually pulled him off Gifford.

Attorney James McGraw says he has represented Williams before but hasn't been contacted by him about the assault charge.

The Post-Standard reports police aren't yet sure if Gifford was the victim of a so-called "knockout game."

Two Syracuse teens were sentenced to prison earlier this year for their roles in the beating death of a 51-year-old man attacked at random.