Published: Feb 17, 2012 12:11 PM EST

LONG BEACH, Calif. (AP) - A federal immigration agent shot and wounded a colleague at their office, before the gunman was killed by a third agent, the FBI says.
 
Several shots were fired about 5:30 p.m. Thursday in the Immigration Customs Enforcement office, leaving one man wounded, said Steven Martinez, assistant director in charge of the FBI's Los Angeles office.
 
"Another agent, working nearby, intervened and fired his weapon to prevent additional rounds being fired at the victim," he said.
 
The gunman died at the scene and the wounded man was taken to a hospital, where he was in stable condition.
 
Authorities released no details about what led to the initial shooting other than to say it was a case of workplace violence involving two federal agents.
 
But the Los Angeles Times, citing multiple law enforcement sources, said the initial shots were fired by an agent at his supervisor during an unspecified dispute.
 
The names of the dead gunman, the victim and the agent who fired the final rounds were not released.
 
There were conflicting early reports about the number of people shot, with local authorities saying two were dead and one wounded, while ICE said one was dead and one wounded.
 
The shooting happened on the seventh floor of the Glenn M. Anderson Federal Building in downtown Long Beach that houses ICE, the Internal Revenue Service and the U.S. Probation and Parole Office.
 
The wounded agent was hospitalized in stable condition, said ICE Special Agent in Charge Claude Arnold.
 
St. Mary's Medical Center Trauma Director James Murray told KCAL-TV that the injured agent sustained wounds to multiple parts of his body, but did not further specify. He said the victim's vital signs were "good for now," and that he had ongoing bleeding but that it wasn't a cause for concern.
 
"At times like this words honestly seem inadequate. When something like this happens in our offices, it's incomprehensible, Arnold said.
 
Along with the FBI, the shooting was being investigated by ICE's Office of Professional Responsibility and Long Beach police.