Two firefighters were killed when they were shot as they responded to a wildfire on an Idaho mountain that authorities say was set to lure them into an ambush, the local sheriff said. It happened in Coeur d'Alene, Idaho, on Sunday.

A SWAT team responding to the scene later found a dead man and a firearm nearby on the mountain where the fire had broken out, the Kootenai County Sheriff's Office said Sunday night. It was not immediately clear if the dead man was the suspect or if there were other suspected shooters still at large, but the sheriff's office did lift a shelter in place order that had previously been in place.

Kootenai County Sheriff Robert Norris said at an earlier news conference Sunday afternoon that first responders had been "actively taking sniper fire as we speak."

"We still have civilians that are coming off of that mountain. We might have civilians that are stuck or in shock on that mountain, so this is a very, very fresh situation," Norris said, adding, "We are prepared to neutralize this suspect who is currently actively shooting at public safety personnel. We are prepared to neutralize this suspect as quickly as possible."

The Coeur d'Alene Fire Department confirmed two of its members were killed and their bodies would be escorted to Spokane, Washington, on Sunday night. Kootenai Health in Coeur d'Alene told CBS News three people were brought to the hospital; two were dead on arrival and a third was being treated as of Sunday night. Details on the living person's condition were not provided and none of the three were identified.

"It appears that modern-day sporting rifles are being used. It appears that high-powered rifles are being used," Norris said at the news conference.

Helicopters with heat-seeking technology were flying over the area trying to locate the shooter or shooters, according to a law enforcement source. But they were having trouble due to a combination of smoke from the wildfire and the presence of hikers and others on the mountain who had been ordered to shelter in place and are also being detected by the technology, the source told CBS News.

Local emergency officials declared a no-fly zone in the area, which applies to drones, noting they "pose a serious risk to firefighting and law enforcement operations."

The Kootenai County Sheriff's Office said in a statement that shots were fired about half an hour after firefighters responded to a fire on Canfield Mountain. 

The wildfire was still burning as of 8:15 p.m. local time.

FBI Deputy Director Dan Bongino said the FBI was on the way to provide "tactical and operational support."

"This is a heinous direct assault on our brave firefighters," Idaho Gov. Brad Little said on social media. "I ask all Idahoans to pray for them and their families as we wait to learn more. Teresa and I are heartbroken. As this situation is still developing, please stay clear from the area to allow law enforcement and firefighters to do their jobs."

Coeur d'Alene is close to the Idaho-Washington border and about 30 miles from Spokane.

This is a developing story. Check back for updates.

Pat Milton contributed to this report.