Eric Tucker, Associated Press

Security personnel respond near the Washington Navy Yard where a gunman was reported in Washington, on Monday, Sept. 16, 2013. (AP Photo/Manuel Balce Ceneta)

WASHINGTON (AP) — Navy firefighters who responded to the Washington Navy Yard shooting had faulty radios that hindered their communications, a union leader said Friday.

Greg Russell, the president of the union that represents civilian Navy firefighters in the Washington, D.C., region, said the radio malfunctions were described to him by multiple firefighters who responded to Monday’s massacre. Former Navy reservist Aaron Alexis killed 12 people at the Navy Yard before being slain in a police shootout.

Russell said the problems prevented firefighters inside Building 197, where the shooting occurred, from communicating with each other and were so bad that the department had to send one of its officials outside the building to transmit messages and commands.

“We’re our own fire department. We need to have our own radio system. It needs to work,” Russell said, adding that the radio system has long been problematic.

The firefighters were ultimately able to use the radio system of local first responders, Russell said. He said the problems caused unnecessary delays, though it was not clear what effect those delays may have had.

“Firefighters provide emergency medical services. Cops chase bad guys, we rescue people,” he said.

A spokesman for Naval District Washington did not respond to requests for comment Friday.

The FBI is still investigating why Alexis, a 34-year-old former Navy reservist and an information technology contractor with a history of mental health problems, entered the building Monday morning with a bag, emerged from a bathroom with a sawed-off shotgun and opened fire on workers. The shooting has prompted reviews into military security and employee screening programs.

The Navy installation re-opened on Thursday for normal operations, though the building where the shooting took place remained closed.