Teen shot troopers from behind

A 19-year-old man shot two state troopers seven times with an assault rifle, killing them as they struggled to arrest his father in a remote Alaskan village, authorities say.

Nathaniel Lee Kangas has appeared in court, two days after 26-year-old Trooper Gabriel "Gabe" Rich and 45-year-old Sergeant Patrick "Scott" Johnson were shot dead.

He was charged with two counts of first-degree murder and one count of third-degree assault.

The slayings in the isolated community of Tanana underscore the challenges law enforcement faces in this huge state. Like many troopers assigned to patrol multiple villages, Rich and Johnson were based outside the community, in their case in a four-person rural service unit in Fairbanks 209km to the east.

They had flown to the community of 238 people to arrest Kangas's father, Arvin, 58, on charges of driving without a licence and threatening the village's unarmed public safety officer, Mark Haglin.

Haglin had received reports the elder Kangas was driving around the village, even though he doesn't have a valid driver's licence.

After Haglin approached Arvin Kangas at his home, the elder Kangas pointed to a rifle and suggested he would use it if Haglin didn't leave, according to the charging document.

Haglin contacted state troopers, who obtained an arrest warrant and accompanied him to Arvin Kangas's home a day after the confrontation.

Arvin Kangas refused to co-operate and tried to run inside, according to the charging document. The troopers pursued, and a scuffle ensued.

Nathaniel Kangas appeared with an assault rifle and shot them, according to the charging document. He then pointed the weapon at Haglin, but lowered it and Haglin was able to flee.

Haglin called for help, and with the aid of other community members, was able to detain Nathaniel Kangas until more troopers arrived, the document says.

Both Rich and Johnson had recently appeared on a cable TV reality show about the Alaska State Troopers.