Two FBI special agents were killed during a training exercise in Virginia, officials said.

Agents Christopher Lorek, 41, and Stephen Shaw, 40, both from the elite Hostage Rescue Team, were killed off the coast of Virginia Beach on Friday, according to the FBI.

The agency did not release additional details, but WAVY-TV reported that the accident involved a helicopter flying near a military command ship.

“We mourn the loss of two brave and courageous men,” FBI Director Robert Mueller said. “Like all who serve on the Hostage Rescue Team, they accept the highest risk each and every day, when training and on operational missions, to keep our nation safe.”

Trained in military tactics, the Hostage Rescue Team is part of the Critical Incident Response Group based at Quantico in northern Virginia.

The team is deployed quickly to trouble spots and provides hostage-situation assistance to local FBI offices. ,