Stinger, a member of Constitutional Patriots New Mexico Border Ops Team militia is pictured on patrol at the US-Mexico border near Mt. Christo Rey in Sunland Park, New Mexico on March 20, 2019. - The militia members say they will patrol the US-Mexico border near Mt. Christo Rey, "Until the wall is built." In recent months, thousands of Central Americans have arrived in Mexico in several caravans in the hope of finding a better life in the United States. US President Donald Trump has branded such migrants a threat to national security, demanding billions of dollars from Congress to build a wall on the southern US border. (Photo by Paul Ratje / AFP)        (Photo credit should read PAUL RATJE/AFP/Getty Images)
PHOTO: PAUL RATJE/AFP/Getty Images
Stinger, a member of Constitutional Patriots New Mexico Border Ops Team militia is pictured on patrol at the US-Mexico border near Mt. Christo Rey in Sunland Park, New Mexico on March 20, 2019. - The militia members say they will patrol the US-Mexico border near Mt. Christo Rey, "Until the wall is built." In recent months, thousands of Central Americans have arrived in Mexico in several caravans in the hope of finding a better life in the United States. US President Donald Trump has branded such migrants a threat to national security, demanding billions of dollars from Congress to build a wall on the southern US border. (Photo by Paul Ratje / AFP) (Photo credit should read PAUL RATJE/AFP/Getty Images)
Now playing
02:31
Armed militia group detains migrants at the border
A view of Capitol Hill during heightened security concerns over possible protests or violence tomorrow March 3, 2021, in Washington, DC. - Washington's security posture has been bolstered after threats of a possible March 4, 2021, "breach" of the US Capitol, with the House of Representatives changing its voting plans to avoid gathering members on a day of potential unrest. (Photo by Brendan Smialowski / AFP) (Photo by BRENDAN SMIALOWSKI/AFP via Getty Images)
PHOTO: Brendan Smialowski/AFP/Getty Images
A view of Capitol Hill during heightened security concerns over possible protests or violence tomorrow March 3, 2021, in Washington, DC. - Washington's security posture has been bolstered after threats of a possible March 4, 2021, "breach" of the US Capitol, with the House of Representatives changing its voting plans to avoid gathering members on a day of potential unrest. (Photo by Brendan Smialowski / AFP) (Photo by BRENDAN SMIALOWSKI/AFP via Getty Images)
Now playing
03:18
Rep. Sarbanes: Failure to pass HR 1 'would split our democracy in two'
Senior Advisor to the President Jared Kushner  attends a press conference on September 4, 2020, in the Brady Briefing Room of the White House in Washington, DC. (Photo by Brendan Smialowski / AFP) (Photo by BRENDAN SMIALOWSKI/AFP via Getty Images)
PHOTO: BRENDAN SMIALOWSKI/AFP/AFP via Getty Images
Senior Advisor to the President Jared Kushner attends a press conference on September 4, 2020, in the Brady Briefing Room of the White House in Washington, DC. (Photo by Brendan Smialowski / AFP) (Photo by BRENDAN SMIALOWSKI/AFP via Getty Images)
Now playing
02:50
Jared Kushner disappears from Trump's inner circle
PHOTO: CBS Evening News with Norah O'Donnell
Now playing
02:14
Governor Cuomo accuser Charlotte Bennett speaks out
In this Dec. 1, 2020 file photo, Chairman of the Federal Reserve Jerome Powell appears before the Senate Banking Committee on Capitol Hill in Washington.  Powell told Congress on Wednesday, Feb. 24, 2021,  that the central bank will not begin raising interest rates until the Fed believes it has reached its goals on maximum employment  and warned that many people in the hardest hit industries will likely need to find different jobs.  (AP Photo/Susan Walsh, Pool, File)
PHOTO: Susan Walsh/AP
In this Dec. 1, 2020 file photo, Chairman of the Federal Reserve Jerome Powell appears before the Senate Banking Committee on Capitol Hill in Washington. Powell told Congress on Wednesday, Feb. 24, 2021, that the central bank will not begin raising interest rates until the Fed believes it has reached its goals on maximum employment and warned that many people in the hardest hit industries will likely need to find different jobs. (AP Photo/Susan Walsh, Pool, File)
Now playing
02:18
Jerome Powell: US economy 'some time' away from full recovery
A customer wears a face mask while shopping for flowers displayed for sale from a wholesale merchant ahead of the Valentine's Day holiday at the Southern California Flower Market on February 12, 2021 in Los Angeles, California. - While some florists note an increased demand for socially distant gifts, the Covid-19 pandemic has impacted global supply chains and shut down most large events including weddings where flowers are popular. The Valentine's Day and Mother's Day holidays are historically the two busiest days of the year for floral businesses. (Photo by Patrick T. FALLON / AFP) (Photo by PATRICK T. FALLON/AFP via Getty Images)
PHOTO: Patrick T. Fallon/AFP
A customer wears a face mask while shopping for flowers displayed for sale from a wholesale merchant ahead of the Valentine's Day holiday at the Southern California Flower Market on February 12, 2021 in Los Angeles, California. - While some florists note an increased demand for socially distant gifts, the Covid-19 pandemic has impacted global supply chains and shut down most large events including weddings where flowers are popular. The Valentine's Day and Mother's Day holidays are historically the two busiest days of the year for floral businesses. (Photo by Patrick T. FALLON / AFP) (Photo by PATRICK T. FALLON/AFP via Getty Images)
Now playing
02:39
States rolling back Covid-19 safety measures as cases continue to rise
PHOTO: CBS' 60 Minutes+/Getty Images
Now playing
01:45
'QAnon Shaman' says he has one regret about January 6
psaki
PHOTO: CNN
psaki
Now playing
00:56
Psaki fires back at Trump testing czar over vaccine claims
Now playing
02:30
Alabama governor explains why she's ending mask mandate
PHOTO: CNN
Now playing
01:35
See what security looks like outside US Capitol
Now playing
00:00
Bash: This is why key GOP senator is fighting Biden's stimulus
PHOTO: YouTube/Everyday Astronaut
Now playing
01:19
Watch SpaceX Mars prototype rocket nail landing, explode on pad
WASHINGTON, DC - JANUARY 16:  Physician to U.S. President Donald Trump Dr. Ronny Jackson listens during the daily White House press briefing at the James Brady Press Briefing Room of the White House January 16, 2018 in Washington, DC. Dr. Jackson discussed the details of President TrumpÕs physical check-up from last week.  (Photo by Alex Wong/Getty Images)
PHOTO: Alex Wong/Getty Images
WASHINGTON, DC - JANUARY 16: Physician to U.S. President Donald Trump Dr. Ronny Jackson listens during the daily White House press briefing at the James Brady Press Briefing Room of the White House January 16, 2018 in Washington, DC. Dr. Jackson discussed the details of President TrumpÕs physical check-up from last week. (Photo by Alex Wong/Getty Images)
Now playing
03:14
DOD releases scathing review of former White House physician
PHOTO: CNN/Getty
Now playing
02:10
'Highly misleading at best': Dale reacts to Pence's op-ed
PHOTO: Gov. Cuomo's office
Now playing
03:35
Gov. Andrew Cuomo addresses women's allegations
Commanding General District of Columbia National Guard Major General William J. Walker testifies before the Senate Homeland Security and Governmental Affairs/Rules and Administration hearing to examine the January 6, 2021 attack on the US Capitol on Capitol Hill on March 3, 2021 in Washington, DC. (Photo by Greg Nash / POOL / AFP) (Photo by GREG NASH/POOL/AFP via Getty Images)
PHOTO: GREG NASH/POOL/AFP via Getty Images
Commanding General District of Columbia National Guard Major General William J. Walker testifies before the Senate Homeland Security and Governmental Affairs/Rules and Administration hearing to examine the January 6, 2021 attack on the US Capitol on Capitol Hill on March 3, 2021 in Washington, DC. (Photo by Greg Nash / POOL / AFP) (Photo by GREG NASH/POOL/AFP via Getty Images)
Now playing
03:01
DC National Guard commander: 'Unusual' Pentagon restrictions slowed response to Capitol riot
Supporters of President Donald Trump hold up their phones with messages referring to the QAnon conspiracy theory at a campaign rally at Las Vegas Convention Center on February 21, 2020 in Las Vegas, Nevada.
PHOTO: Mario Tama/Getty Images
Supporters of President Donald Trump hold up their phones with messages referring to the QAnon conspiracy theory at a campaign rally at Las Vegas Convention Center on February 21, 2020 in Las Vegas, Nevada.
Now playing
03:00
Hear why QAnon supporters believe Trump will be president on March 4th
(CNN) —  

The FBI has arrested a member of an armed militia that had detained hundreds of migrants at the border this week, the New Mexico attorney general’s office said Saturday.

Larry Mitchell Hopkins, 69, is a member of an armed group that had reportedly detained migrants near Sunland Park, New Mexico, state Attorney General Hector Balderas said in a statement.

Hopkins – also known as Johnny Horton Jr. – was arrested on felony charges of being in possession of firearms and ammunition, according to a statement from the FBI’s Albuquerque field office.

Larry Mitchell Hopkins
PHOTO: Doña Ana County Detention Center
Larry Mitchell Hopkins

Earlier this week, videos posted online purported to show migrants being held by a militia known as the United Constitutional Patriots before being turned over to US Border Patrol.

The footage prompted a condemnation from the American Civil Liberties Union of New Mexico, which in a letter likened the militia’s actions to kidnapping.

“This is a dangerous felon who should not have weapons around children and families,” Balderas said. “Today’s arrest by the FBI indicates clearly that the rule of law should be in the hands of trained law enforcement officials, not armed vigilantes.”

Hopkins is expected to make a first appearance in court on Monday, the FBI said. CNN was unable to determine Saturday whether he was represented by an attorney.

CNN has reached out to the United Constitutional Patriots for comment, but has not heard back.

A spokesman for the group previously said their actions were legal, “comparing the detention of the migrants to ‘a verbal citizen’s arrest,’” according to a report from The New York Times.

Videos show armed men in masks, fatigues

Various private militia groups – often espousing anti-immigrant views – have patrolled the border for years, but it’s rare to see footage of an armed group detaining migrants on the US side of the border.

Videos purported to show members of the group detaining migrants, including families with children, who have just crossed the border.

CNN has reached out to the group and the individuals who posted the videos for comment but has not confirmed details about who shot the videos, or when and where they were recorded.

In the footage, people wearing full military fatigues can be seen with handguns strapped to their sides, wearing gloves and black face masks. Armed men order the migrants to stop, force them to sit on the ground and then appear to call Border Patrol to pick the migrants up.

In at least two videos posted on the group’s Facebook page, a man in fatigues verbally identifies himself as “Border Patrol” when stopping a group of migrants.

A US Customs and Border Protection spokeswoman declined to comment on the United Constitutional Patriots and the online videos, but said the agency “does not endorse or condone private groups of organizations taking enforcement measures into their own hands.”

CNN’s Catherine Shoichet, Rebekah Riess, Deanna Hackney, Geneva Sands and Paul P. Murphy contributed to this report.