Three people were killed after two firefighting helicopters crashed mid-air while responding to a brush fire in Riverside County on Sunday night.

The crash happened in a remote area near Pipeline Road and Apache Trail in Cabazon around 7:30 p.m., according to the Riverside County Sheriff’s Department.

The Morongo Casino Resort & Spa is located about a mile away from the crash site.

The three victims included a CAL FIRE division chief, a CAL FIRE fire captain, and a contract pilot, authorities confirmed in a Sunday night press conference. Their names and ages were not released.

During the mid-air crash, one helicopter was able to safely land without injuries while the second helicopter crashed, killing all passengers onboard.

The collision caused an additional four-acre brush fire which was later extinguished, officials said.

Fire crews were battling a 20-acre fire called the Broadway Fire that had spread from a structure fire near Broadway Street and Esperanza Avenue earlier that night.

Both helicopters involved crews that were contracted with CAL FIRE to fight fires across the state.

“I would like to express our deepest sympathies and sorrow to the families and the coworkers of the personnel,” said a CAL FIRE/Riverside County Fire spokesperson. “This was a tragic loss for the community. We think about this and how it affects the families. They have lost three great individuals — three fathers, three husbands, three friends, three sons. We want to tell everyone while their sacrifice should not be in vain, that we think about them and we will support them.”

The circumstances surrounding the crash remain under investigation.

Authorities initially indicated the helicopter that crashed was a water-dropping aircraft. A public information officer Monday morning told KTLA that the crashed chopper was actually an observation helicopter.

The National Transportation Safety Board has taken over the investigation.