LONG BEACH, Calif. (KABC) -- Three men are dead and nine others were injured after what police believe was a targeted attack at a Halloween party in the Rose Park neighborhood of Long Beach Tuesday night.Authorities responded to the mass shooting at about 10:45 p.m. when gunfire erupted at a party in the 2700 block of 7th Street, near Temple Avenue.The Long Beach Fire Department said three men were dead at the scene and nine were transported in what paramedics described as a mass casualty incident, with 12 patients reported.Seven of the nine transported are women between the ages of 20 to 49 years old. A family member of one of the victim's told Eyewitness News the party was for employees from the Hollywood Park Casino in Inglewood. His sister was hospitalized with two gunshot wounds but was in stable condition.Police say multiple people were dressed in costumes when a shooter, who remains at large, started firing rounds.Footage from AIR7 HD showed paramedics treating the injured patients at a yard next to a nail salon before they were transported.Three suspects remain at large. A suspect description was not available. An investigation is ongoing.