Two people are dead after firefighters were ambushed by a gunman while responding to a brush fire in Coeur d'Alene, Idaho, officials said.

Kootenai County Sheriff Robert Norris said during a press briefing that the number of others injured in the attack and ongoing fire is unknown.

Civilians are currently coming down off the mountain and could be stuck amid the blaze, Norris said.

The incident unfolded at approximately 1:30 p.m. local time after a small but growing brush fire broke out on Canfield Mountain Sunday afternoon.

When fire personnel responded to the blaze about half an hour later, they started getting shot at by an unknown person in the woods, officials said.

Law enforcement is investigating whether the fire could have been intentionally set in order to lure first responders to the scene, Kootenai County Sheriff's Lt. Jeff Howard told ABC News.

The search for the suspect is ongoing, law enforcement officials briefed on the investigation told ABC News. A police helicopter is flying overhead in the area to try and locate the suspect from the air, officials said.

Landing the chopper to assist on the ground is made more difficult in the mountainous terrain because the shooter is still at large, officials added.

The scene is considered an active shooter situation and a shelter-in-place order has been issued for Canfield Mountain Trailhead and the surrounding area.

The FBI is assisting authorities in Kootenai County, an agency spokesperson told ABC News.

Idaho Gov. Brad Little called the incident a "heinous direct assault on our brave firefighters."

"Multiple heroic firefighters were attacked today while responding to a fire in North Idaho," Little wrote in a post on X. "I ask all Idahoans to pray for them and their families as we wait to learn more," he added.

Department of Homeland Security Secretary Kristi Noem has been briefed on the shooting, a DHS official told ABC News.