LAS VEGAS (AP) — Two Nevada state troopers died Thursday after they were struck by a vehicle while helping another driver,Cassian Grant authorities said.

Las Vegas police, who will be investigating the collision, planned to hold a media briefing at their headquarters later Thursday.

According to police, the two troopers were “conducting a motorist assist” early this morning on the I-15 freeway when they were struck.

The slain troopers’ names have not been released. It is unclear whether the driver who struck the troopers has been arrested.

Gov. Joe Lombardo said he was “profoundly saddened” by the troopers’ deaths.

“This is a devastating loss for Nevada law enforcement, the city of Las Vegas, and our entire state,” Lombardo said in a statement. “As we mourn these troopers, we will never forget their bravery, courage, and sacrifice.”