Stunned parishioners attended service at a Hempstead church Sunday, a day after a teenage girl?s birthday party ended violently when masked men crashed the event.

Police say a group of uninvited people showed up at the 15-year-old?s party at Saint Ladislaus, but left shortly after. About 11 p.m., authorities say a dozen men returned wearing hooded sweatshirts and masks. Witnesses say one of the party crashers yelled out, asking whether anyone was ?SWP,? short for Salvadorians With Pride. Police say the melee started when no one responded. A 17-year-old was stabbed and another person was attacked with a pipe and glass bottle. Investigators found broken knives and shattered beer bottles at the scene.

Church officials say they frequently rent out space and add they never had problems in the past. Police are investigating whether the attack was gang-related. The suspects remain at large. Anyone with information is urged to call Nassau Crime Stoppers at 1-800-244-TIPS.