A 14-year-old boy was busted with a loaded gun during a heated clash inside a Queens playground Wednesday afternoon — and a good Samaritan who stepped in to stop the melee was slashed by another attacker,

The teens skirmished across the street from I.S. 192 The Linden school on 204th St. near Hollis Ave. in St. Albans just before 3:40 p.m., cops said.