A leader of a New Mexico militia that has been detaining migrant families at the U.S.-Mexico border said the group was "training to assassinate George Soros, Hillary Clinton, and Barack Obama," according to an FBI agent's sworn deposition describing reports phoned into the agency's public tip line.

Larry Mitchell Hopkins, 69, who was arrested Saturday on suspicion of being a felon in possession of a firearm and ammunition, made an initial appearance in federal court in Las Cruces, New Mexico, on Monday.

Hopkins remains in custody pending a preliminary hearing and a detention hearing April 29 in Albuquerque, according to the FBI and the U.S. attorney's office.

Hopkins, who also goes by the alias Johnny Horton Jr., has been described as the "commander" of the United Constitutional Patriots, a militia group that has recently been detaining asylum-seeking families at the southern border, drawing outcry from local politicians and activists.

In an affidavit filed Saturday in support of Hopkins' arrest, the FBI agent said that in October 2017, the agency's public access line received reports of "alleged militia extremist activity" in Flora Vista, New Mexico, based out of Hopkins’ home, with the group being supported by about 20 members who were "armed with AK-47 rifles and other firearms."

"Hopkins also allegedly made the statement that the United Constitutional Patriots were training to assassinate George Soros, Hillary Clinton, and Barack Obama, because of these individuals' support of Antifa," the complaint said, referring to so-called anti-fascist activists.

It was not clear when and to whom Hopkins made these statements. Hopkins' attorney, Kelly O’Connell, said his client denies the allegations.

Hopkins, also known as 'Striker,' the leader of the Constitutional Patriots militia, speaks with Viper, right, about logistics in Anapra, New Mexico, on March 20. Paul Ratje / AFP / Getty Images file

"He says that is categorically false that that's what they were doing," O'Connell said. "There was no plan to do any of that."

In late November of 2017, two FBI special agents went to Hopkins’ residence, were invited in and led to a room known as his "office," where they observed about "10 firearms leaning against a wall in a closet in plain view," according to the complaint.

When asked who the firearms belonged to, Hopkins said all the firearms in the home were owned by Fay Sanders Murphy, who lives at the residence and was described as his "common law wife," according to the complaint.

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Hopkins also disclosed to the agents that there were additional weapons in the home, including a shotgun, a handgun in the bedroom and another handgun in the kitchen, according to the complaint.

Both Hopkins and Murphy gave the agents consent to search the residence, the complaint said, and showed them the location of the other firearms.

He walked one agent to the kitchen and brought a black tactical vest and said, "that’s my black right there and it is loaded," according to the complaint. The agents recovered a loaded firearm from a holster attached to the vest, the complaint said.

Larry Mitchell Hopkins Dona Ana County Detention Center

In the master bedroom, Hopkins directed an agent to a loaded Blackhawk 12-gauge shotgun and said, "it is legal, actually that shotgun was given to my wife from one of my men," the complaint said.

The special agent who wrote the complaint said that after searching the residence, he discovered Hopkins had prior felony convictions.

Hopkins' lawyer questioned why his client was arrested Saturday, when the search of his property happened in 2017.

"If it was that outrageous of a crime, why not lock him up right then?" O'Connell said, adding he questioned why "this charge suddenly comes up" while Hopkins was in the public eye over the debate regarding the actions of the United Constitutional Patriots at the border.

In 1996, Hopkins was convicted of possession of a loaded firearm and was sentenced to state prison in Michigan for 16 months minimum to two years maximum, according to the complaint.

In 2006, he was convicted of felony possession of a weapon in Oregon and sentenced to 40 days in jail and 36 months of probation, the complaint said.

At the same time, Hopkins was also convicted of criminal impersonation of a peace officer and sentenced to 20 days in jail and 24 months of probation, the complaint said.

State records confirm Hopkins’ convictions described in the complaint.

Court records show a warrant for Hopkins’ arrest was issued last week.

If convicted, he faces a maximum statutory penalty of 10 years in prison, according to the FBI statement.

The American Civil Liberties Union and New Mexico Gov. Michelle Lujan Grisham have blasted the United Constitutional Patriots for stopping migrants at the border until immigration authorities can apprehend them in recent months.

Customs and Border Protection has said it "does not endorse private groups or organizations taking enforcement matters into their own hands."