(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.
Bundy 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.
To some, the 67-year-old Bundy is a hero who hails from a long family of ranchers stretching back to the Wild West.
To environmentalists and the feds, however, he's an outlaw of sorts who owes U.S. taxpayers more than $1 million in unpaid grazing fees.
The U.S. government is rounding up Bundy's cattle that it says have been grazing illegally on public lands in Clark County for more than 20 years, according to the land-management bureau and the National Park Service.
Between Saturday and Wednesday, contracted wranglers impounded a total of 352 cattle, federal officials said. Bundy says he owns 500 of the more than 900 cattle that federal officials are planning to confiscate for illegal grazing, the Las Vegas Review-Journal reported. Bundy told the newspaper that each head of his livestock is worth about $1,000.
Since the roundups began, protesters have been confined to two areas to publicly declare their grievances, but the peaceful protests in recent days "have crossed into illegal activity, including blocking vehicles associated with the (roundup), impeding cattle movement, and making direct and overt threats to government employees," the two federal agencies said in a statement.
On Wednesday, a bureau truck driven by a civilian employee assisting in the roundup "was struck by a protester on an ATV and the truck's exit from the area was blocked by a group of individuals who gathered around the vehicle," the agencies' statement said.
In the scuffle with protesters, a police dog was kicked, and officers protecting the civilian driver were threatened and assaulted, the two agencies' statement said. "After multiple requests and ample verbal warnings, law enforcement officers deployed Tasers on a protestor," the statement said.
The profanity-laced tussle was captured on a video posted on YouTube. A group that said it posted the video didn't respond to requests for comment.
In the video, protesters demanded to know why a backhoe and a dump truck were being used in the roundup -- and whether any livestock were killed. On Thursday, Lueders said the heavy equipment was used for field restoration.
"No BLM! No BLM!" the protesters chanted to rangers in the middle of a two-lane rural highway.
What sounds likes zapping Tasers can be heard in the video.
In the wake of the publicized protests, members of various militia groups have been traveling from Virginia, Texas, Montana, Idaho and Wisconsin and arriving at the protest site and Bundy's ranch to support the family, said Stephen L. Dean, 45, of Utah, a member of one such group called the Peoples United Mobile Armed Services.
"It's tyranny in government," Dean said when asked what brought him to Nevada.
And, he added, "stealing people's cattle."
One banner at the protest side stated: "Has the West been won? Or has the fight just begun!"
In removing Bundy's livestock from public lands, the park service and land bureau are carrying out two U.S. District Court orders from two different judges.
"Cattle have been grazing in trespass on public lands in Southern Nevada for more than two decades," the National Park Service said. "The BLM and NPS have made repeated attempts to resolve this matter administratively and judicially. Impoundment of cattle illegally grazing on public lands is an option of last resort."
Added the BLM: "Mr. Bundy has also failed to comply with multiple court orders to remove his cattle from the federal lands and to end the illegal trespass."
The bureau does allow grazing on federal lands -- it administers 18,000 grazing permits and leases on 157 million acres across the country, the agency said.
Bundy's dispute with the government began about 1993 when the bureau 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. His family has been ranching since the 1800s, before the U.S. Department of Interior was created and endangered species became a federal issue, he said in an interview with KLAS.
"My forefathers have been up and down the Virgin Valley ever since 1877. All these rights I claim have been created through pre-emptive rights and beneficial use of the forage and the water. I have been here longer. My rights are before the BLM even existed," Bundy told the station.
"With all these rangers and all this force that is out here, they are only after one man right now. They are after Cliven Bundy. Whether they want to incarcerate me or whether they want to shoot me in the back, they are after me. But that is not all that is at stake here. Your liberty and freedom is at stake," he continued.
And Bundy sees it as a state issue.
"The federal government has seized Nevada's sovereignty ... they have seized Nevada's laws and our public land. We have no access to our public land and that is only a little bit of it," he said.
This week, Nevada Gov. Brian Sandoval told the bureau of residents' criticism of the roundup.
What Sandoval said he found "most disturbing" was the BLM's use of a "First Amendment area" that confined protesters to a designated area.
Such an area "tramples upon Nevadans' fundamental rights under the U.S. Constitution," Sandoval said. "No cow justifies the atmosphere of intimidation which currently exists nor the limitation of constitutional rights that are sacred to all Nevadans." In response, federal officials are allowing the protesters to gather on public lands as long as they don't impede the roundup, said Lueders, the BLM's director in Nevada.
Bundy is digging in for a long fight.
"I've been fighting this for a number of years. It's not about my cows, I'll tell you that much," he said at a town meeting on Wednesday night. "It's about freedom and liberty and our Constitution ... and above all it's about our policing power. Who has policing power today?"
With the growing controversy, it was uncertain Thursday how long the cattle roundup will now last. At Wednesday night's meeting, residents gave Bundy a standing ovation when he publicly spoke.
"I love you people. And I love this land, and I love freedom and liberty," Bundy told the crowd. "I know without doubt that our Constitution didn't provide for anything like the federal government owning this land, and so when I pay my grazing fees -- if I owe any grazing fees -- I will sure pay it to the right landlord, and that will be to Clark County, Nevada."
CNN's Dottie Evans and Carma Hassan contributed to this report. Dan Simon and Chuck Conder contributed from Nevada. Michael Martinez wrote from Los Angeles.