Two crewmen aboard an Idaho National Guard AH-64D Apache helicopter were killed after the chopper crashed just outside of Boise on Thursday evening.

KBOI reported that military officials said the pilots were on a training mission when the helicopter went down near the Boise Airport.

“The men and women of the Idaho National Guard are united in grief at the loss of two of our brothers in arms, who gave their lives while training to defend our nation,” said Idaho National Guard Commander, Major General Gary Sayler. “Today, our thoughts and prayers are with their families.”

The names of victims have not been released at this time and the cause of the crash is under investigation.

The crash was the second U.S. military air accident of the day. Hours before, an Air Force F-16 fighter jet crashed in the Gulf of Mexico about 50 to 75 miles south of Panama City. Search and rescue crews were able to recover the body of the deceased airman in the Gulf waters.