CHELSEA ? A Revere man and his cousin were shot inside a Chelsea music studio Saturday night during a simultaneous birthday party and music video recording session, police said.Chelsea Police Capt. Keith Houghton said the two victims are in their early 20s and suffered non life-threatening injuries.Investigators believe the shooter fired a single bullet at close range as the victims stood behind a DJ booth. The bullet grazed one man’s shoulder then continued flying and struck the Revere man in the buttocks about 11:30 p.m.”Only one bullet was recovered at the scene,” Houghton said.Police have not released the victim’s full identities but said numerous Lynn and Revere residents were present.Police estimated about 70 people were inside the licensed music studio, at 311 Broadway, for what Houghton described as a birthday party where videographers were filming scenes for a hip-hop music video. Houghton said he did not know if any artists were at the scene of the shooting or the name of the artists whose music video was being recorded.Police said several witnesses fled the area after the gunshot was fired but investigators managed to question 31 people at the scene.Houghton said the shooting might be gang-related and that police have identified two suspects.”We’re pretty confident we know who the suspects are,” Houghton said.Houghton added that when officers first arrived on the scene, a YouTube.com video was playing on a large-screen projector. Partygoers had been watching an amateur video that showed illegal street racing on Eastern Avenue in Chelsea.”It was like ?American Graffiti,'” said Houghton, referring to the 1973 film.He said the video showed large groups gathered on the road in the middle of the night. One person would stand on the double yellow line and wave a flag to start the race, which had cars driving on both sides of the road and into oncoming traffic.”We’re actually taking this YouTube video and examining it,” Houghton said. “We’ve have constant problems with drag racing.”Houghton said a Stoneham man recently opened the studio and it is properly licensed. The owner signed a two-year lease that began in 2008.”The owner has been very cooperative,” Houghton said.As of Sunday night the shooting suspects were still on the loose.