(AP) — Two FBI special agents on the agency’s elite Hostage Rescue Team have been killed in a training accident in Virginia.

The FBI’s national press office said in a statement Sunday that the accident happened off the coast of Virginia Beach on Friday. No other details were given and the cause is under investigation.

The special agents were identified as 41-year-old Christopher Lorek and 40-year-old Stephen Shaw,

FBI Director Robert Mueller said in the statement that “we mourn the loss of two brave and courageous men” and “our hearts are with their wives, children and other loved ones who feel their loss most deeply.”

The Hostage Rescue Team is part of the Critical Incident Response Group based at Quantico in northern Virginia.