BOISE, Idaho – Authorities say two firefighters were killed and another was badly injured after they were ambushed and shot while responding to a wildfire near Coeur d’Alene, Idaho, on Sunday afternoon.

Here’s what to know about the attack, the investigation and next steps.

Ambush starts with a brush fire

Kootenai County Sheriff Bob Norris said firefighters first responded to an early afternoon report of a brush fire at Canfield Mountain, a popular and scenic hiking and biking area near the outskirts of town. But once the firefighters arrived, someone began shooting at them.

The fire was set to lure the firefighters into an ambush, Norris said.

Law enforcement officials responded, locking down the neighborhoods near the hiking area and trying to find the shooter in hilly terrain that had plenty of cover, with thick brush and trees and smoke from the fire nearby.

First hours are chaotic, with injuries and number of shooters unknown

Over the next few hours, it wasn’t clear if hikers or other recreationists were stuck on the mountain, or if any civilians had been injured in the shooting, Norris said. What was clear was the danger the firefighters and responding law enforcement faced. They exchanged gunfire with the shooter, he said.

“We don’t know how many suspects are up there, and we don’t know how many casualties there are,” Norris told reporters at a 4:30 p.m. news conference. “We are actively taking sniper fire as we speak.”

A spokesperson with Kootenai Health, later confirmed that three patients were transported to the hospital — two were dead by the time they arrived, and a third was injured.

The deceased included a firefighter from the Coeur d’Alene Fire Department and one from Kootenai County Fire and Rescue. A third firefighter was badly injured but had made it through surgery and was “fighting for his life,” Norris said later that night.

Cell phone data helps law enforcement find the suspect

Faced with more than 17,000 square feet (1,580 square meters) of containment area, part of it burning, authorities used cell phone data to narrow their search. They identified a cell signal around 3:15 p.m. and noticed it had not changed location for some time, Norris said.

A tactical response team went to the location and found a deceased man with a weapon nearby. Officials believe the man was the shooter, the sheriff said.

The fire complicates the crime scene

The fire was burning close to the body of the suspect, and so authorities had to “scoop the body up” before it was engulfed in flames, Norris said.

Crews were stationed around the area overnight and the sheriff said the investigation would continue Monday morning.

Norris said investigators believe that once they are able to fully search the area, they may find that more weapons had been placed by the suspect.

Names and other details have not been released

The names of the slain and injured firefighters have not been released.

Nor has the name of the suspect, whose identity authorities are waiting to confirm, Norris said.

A procession of fire and law enforcement vehicles accompanied the bodies of the fallen firefighters as they were taken from the hospital in Coeur d’Alene to the medical examiner’s office in Spokane, Washington, a neighboring city just across the state line.