ALBUQUERQUE, N.M. – 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 girlfriend of the gunman, Police Chief Ray Schultz said. It was not immediately clear whether she was among the dead.

Chaos unfolded as the 37-year-old 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 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.

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 man carried a handgun, and investigators were trying to determine whether there were additional weapons. No victims’ names have been released.

Schultz said the gunman and his girlfriend had children who live in Rio Rancho and said they were taken into custody by “another agency.” The chief said there had been at least one previous domestic violence call involving the gunman but that it was outside Albuquerque.

He said 226 people were taken 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, but explained at a later news conference that the responding officers had seen people down and believed they were dead, then continued into the building to look for the gunman. He characterized this as standard practice when there could be an active gunman at a crime scene..

Emcore manufactures components that allow voice, video and data transmission over fiber optic lines. It also makes solar power systems for satellite and ground-based systems.

Based in Albuquerque, the company has about 700 full-time employees.