Worcester police on Monday identified a man who died after a fight at a condominium complex early Sunday morning. Robert Walker, 18, of Blackstone, died following an altercation with Michael Ventura, 18, of Worcester, police said in a statement. An argument between the two began at a party at the Crestwood Arms complex and moved outside, where Ventura struck Walker with a bottle, police said. Walker fled, and was later found unresponsive on the property and taken to a hospital where he was pronounced dead. The cause has not yet been determined. Ventura was charged with aggravated assault and battery with a dangerous weapon that caused serious bodily injury.