The armed occupiers of a wildlife reserve in Oregon were given “ample opportunity” to leave peacefully before their leaders were arrested and one of them killed, police have said.
The anti-government protesters were to blame for the violence, said officials.
The militia took over the refuge to protest about ranchers jailed for setting fire to federal land.
Federal agents have sealed off the site to try to flush out the remaining number still holed up at the reserve.
One man was killed and eight arrested at a traffic stop on Tuesday night.
Police would not release the name of the man but said he died as authorities tried to take him into custody.
He was named by his daughter as Robert “LaVoy” Finicum, a 55-year-old rancher from Cane Beds, Arizona.
The armed protesters “have chosen to threaten and intimidate the America they profess to love,” said Greg Bretzing, the FBI’s Portland special agent in charge.
Three weeks ago, the group took over the wildlife refuge, claiming the government has been taking land illegally from ranchers for decades.
Witnesses have said the man killed by police charged at them, while others say he complied with authorities’ orders.
“Through criminal actions, they’ve brought these consequences upon themselves,” said Mr Bretzing.
“We will continue to look for safe procedures on how to bring this to a peaceful conclusion.”
Harney County Sheriff Dave Ward said the traffic stop “ended badly” but it did not have to happen.
He said the occupation has been tearing the community apart and it is time for the protesters to leave the nature reserve.
Those who were arrested will have a court appearance on Wednesday.
The Oregon stand-off
How did it begin?
In October, a federal judge ruled the sentences on two Oregon ranchers, Dwight and Steven Hammond, for burning federal land were too short and jailed them for about four years each.
Angered by the ruling, Nevada native Ammon Bundy began a social media campaign backing them and travelled to Burns, Oregon, organising meetings.
His group attracted supporters from across a number of states and Mr Bundy called it Citizens for Constitutional Freedom. On 2 January the armed militiamen took over the Malheur National Wildlife Refuge – and widened the range of demands.
What are the militia’s aims?
It is an extension of the Sagebrush Revolution of the 1970s and 1980s that demanded the transfer of federal land in many western states to local control.
Mr Bundy’s own father – a Nevada rancher – had been involved in a protest over cattle-grazing rights in 2014. One policy is to try to persuade ranchers to tear up their federal grazing contracts.
Although many local residents are sympathetic with its cause, many also oppose the occupation of the refuge. Even the local ranchers who are serving the longer sentences distanced themselves from the militia.
How has the FBI responded?
Initially in a low-key manner. The FBI was fearful of a repetition of the bloody end to the siege at Waco in Texas in 1993.
Local and state officials had demanded the FBI do more.
Are militias legal?
The term has a complex history and generally refers to those outside the official military who can be called on in times of need. The US Constitution refers to the president having command of “militia of several states” and that Congress “can call forth militia” to tackle insurrection and invasion.
Those who form such militias cite the constitution and various references in federal and state law as granting them legality.