(CNN) -- A 20-year dispute between a Nevada rancher and federal rangers over illegal cattle grazing erupted into an Old West-style showdown on the open range this week, even prompting self-proclaimed members of militia groups from across the country to join the rancher in fighting what they say is U.S. "tyranny."
What began as a legal fight between longtime rancher Cliven Bundy and the U.S. Bureau of Land Management has escalated as Bundy kept his cattle on the federal land, and the government has responded by beginning roundups of the livestock.
A confrontation teetered on violence Wednesday when Bundy family members and dozens of supporters angrily confronted a group of rangers holding Tasers and barking dogs on leashes near Bunkerville, about 80 miles northeast of Las Vegas.
Federal officials say a police dog was kicked and officers were assaulted.
Rancher Cliven Bundy, right, leaves the podium with bodyguards after a news conference near his ranch in Bunkerville, Nevada, on Thursday, April 24. Bundy and the Bureau of Land Management have been locked in a dispute for a couple of decades over grazing rights on public lands.
Chris Shelton of Las Vegas interacts with his 1-week-old son as his mother Shelley Shelton holds his rifle during a Bundy family "Patriot Party" near Bunkerville, Nevada, on April 18.
Bundy family members and supporters of rancher Cliven Bundy set up for a "Patriot Party" on April 18. The family organized the party to thank people who supported Cliven Bundy in his dispute with the Bureau of Land Management. 
Cattle rancher Cliven Bundy talks to his supporters Friday, April 11, in Bunkerville, Nevada. They had been protesting the federal government's roundup of Bundy's cattle, which led to an Old West-style showdown last week. The government says Bundy's livestock has been illegally grazing on U.S. lands for 20 years. Bundy says his family's cattle has grazed on the land since the 1800s.
Brand Thornton carries a rifle at a protest site in Bunkerville on April 11. The controversy drew armed militia groups from across the country to Bundy's side. The Bureau of Land Management stopped rounding up Bundy's cattle on Saturday, April 12, and it says it returned about 300 head of cattle to the open range to avoid the potential for violence.
People gather at a protest area along State Route 170, near the cattle roundup on April 11.
A sign announces the closure of public land during the cattle roundup. 
Krissy Thornton, right, and Burgundy Hall protest the cattle roundup on Wednesday, April 9. 
Thornton, right, looks at a wound on Bundy's son Ammon on April 9. Bundy family members and dozens of supporters angrily confronted a group of rangers holding Tasers and barking dogs on Wednesday. Bundy family members say they were thrown to the ground or jolted with a Taser. Federal officials say a police dog was kicked and officers were assaulted.
The U.S. government was rounding up cattle that it says have been grazing illegally on public lands for more than 20 years, according to the Bureau of Land Management and the National Park Service. The Bureau of Land Management said Cliven Bundy owed about $1 million in back fees.
Cliven Bundy, left, and his son Dave talk to a reporter in Las Vegas on Monday, April 7. Bundy's dispute with the government began two decades ago, when the Bureau of Land Management changed grazing rules for the 600,000-acre Gold Butte area to protect an endangered desert tortoise, KLAS reported. Bundy refused to abide by the changes and stopped paying his grazing fees to the federal bureau, which he contends is infringing on state rights.
People help erect a pole so that they could hang a banner April 7 in support of Bundy. One banner at the protest side stated: "Has the West been won? Or has the fight just begun!"
Rancher Derrel Spencer speaks during a rally in support of Bundy on April 7.
Chris Miller holds his hand over his heart during a rally in support of Bundy on April 7.
Bundy's son Arden works at his father's ranch on Saturday, April 5.
Cliven Bundy, right, and Clance Cox stand at the Bundy ranch on April 5.
Bundy walks by a free speech area set up by the Bureau of Land Management on Tuesday, April 1.
Federal rangers block a road near Bunkerville, about 80 miles northeast of Las Vegas, on April 1.
Photos: Showdown in NevadaBundy family members say they were thrown to the ground or jolted with a Taser.
In the end, the rangers got into their white SUVs and drove away, a YouTube video of the incident showed.
"Get out of our state!" the cheering protesters yelled at the rangers as they departed in several vehicles. "BLM go away! BLM go away!" they added, referring to the Bureau of Land Management.
The entire incident is now under investigation, Amy Lueders, the bureau's director in Nevada, said Thursday.
