Philadelphia, New York, Boston weather: tornado watch issued

Over the Memorial Day weekend, a large number of young people — possibly as many as 1,000, drawn together by Facebook and Twitter — gathered along the sandy strip in South Boston. It was perfect beach weather, after all. However, fighting broke out, triggering a law enforcement response that ultimately involved five agencies.

Rival gangs instigated the fights, according to State Police, who have jurisdiction over that stretch of land. But in a rare public break with law enforcement colleagues, Boston Police Commissioner Edward F. Davis rejected the gang-related label.

“Our best intelligence is that there were a lot of kids on the beach. A fight broke out between two groups of girls, and expanded to a bunch of men,’’ said Davis in a telephone interview. “It was a very disturbing incident that needed to be brought back into line. But it’s problematic when you start to talk about a thousand gang members invading the beach . . . To be very precise, Carson Beach is safe.’’