ALBUQUERQUE, NM --A former employee opened fire at an Albuquerque fiber optics manufacturer Monday, killing two people and wounding four others before turning the gun on himself in what police called a domestic violence dispute. The shooting at Emcore Corp. appeared to involve the 37-year-old gunman's girlfriend, police Chief Ray Schultz said. It was not immediately clear whether she was among the dead. Chaos unfolded as the gunman opened fire, sending employees fleeing for cover as police locked down the entire neighborhood. Police were alerted to the shooting shortly before 9:30 a.m. Five officers were inside the building within three minutes, Schultz said. The Emcore campus was surrounded by police cars, many arriving with sirens wailing, as helicopters circled overhead. The chief called the Emcore campus "a very secure facility" and said it appeared the gunman forced his way into the building and entered several areas. Schultz said detectives and FBI agents were reviewing surveillance video. "It was a large and complex shooting scene," he said. Schultz said one victim who confronted the gunman was found dead outside the building. The other victims included the gunman, who was found inside, and a person who died at University Hospital. Schultz said the gunman carried a handgun, and investigators were trying to determine if there were additional weapons. No victims' names have been released, and an investigation was continuing. Schultz said the gunman and his girlfriend had children who live in Rio Rancho and said the youths were taken into custody by "another agency." The chief said there was at least one previous domestic violence call involving the gunman but that it was outside Albuquerque. He said 226 people were transported by bus from Emcore buildings to a community center, where detectives interviewed them. Employees also were offered grief counseling and treatment for asthma or diabetic conditions. Schultz initially said six were dead, then explained at a later news conference later that the responding officers had seen people down and believed they were dead, then continued into the building to search for the gunman. He characterized it as standard practice when a crime scene could have an active shooter. "You work to get the shooter contained, then you triage the victims. That's what happened here," Schultz said. Officers who arrived later determined some shooting victims had survived. Schultz also said there was confusion at University of New Mexico hospital, where one victim died but was reported as two deaths. Emcore manufactures components that allow voice, video and data transmission over fiber optic lines. They also manufacture solar power systems for satellite and ground-based systems. Based in Albuquerque, the company has about 700 full-time employees. In January, a disgruntled worker embroiled in a pension dispute with ABB Group in St. Louis killed three people and wounded five others before killing himself at a company plant. That month in Kennesaw, Ga., a disgruntled employee killed three people and shot two others at a Penske truck rental office. Of the 5,071 workplace fatalities in 2008, 517 were homicides, or about 10 percent of all workplace fatalities that year, according to U.S. Department of Labor Statistics. The department reported the 2008 numbers represent an 18 percent drop in workplace homicides from 2007 and a 52 percent drop from 1994, when 1,080 workplace homicides occurred.