Police say it is possible there could be more arrests. They also say some of the people arrested could have ties to a white supremacy group.
NBC News has learned that federal officials are downplaying the arrests, saying when one of the men was arrested, he made a threat against Obama, but they do not believe it was based on any kind of plan or actually intent.
"It looks like one guy just made a remark trying to act important," one federal official told NBC News.
Aurora Police arrested the first man, 28-year-old Tharin Gartrell of Centennial, early Sunday morning after a routine traffic stop. During the traffic stop, officers found two rifles, boxes of ammunition, one rifle scope, a bullet proof vest, walkie-talkies and methamphetamines. Gartrell is being held in the Arapahoe County jail in lieu of $50,000 bond and has a felony criminal record.
Aurora Police says a second man, 32-year-old Nathan Johnson, was arrested at 4:30 a.m. on Sunday at a hotel near Interstate 25 and Belleview Avenue. Johnson is being held by Denver Police.
A third man, 33-year-old Shawn Adolf of Greeley, was arrested at Cherry Creek Hotel in Glendale on Monday. NBC News reports that when police knocked on his hotel door, Adolf jumped out a sixth floor window. He landed on an awning and then jumped down to the ground, injuring himself. He ran into nearby bushes where officers apprehended him. Authorities say he had weapons.
He was taken to Denver Health Medical Center where he was treated.
Adolf was wanted on seven outstanding warrants totally more than $1 million.
A fourth suspect was also arrested, according to 9NEWS' partners at The Denver Post. The suspect is a juvenile and 9NEWS is not releasing the name because the person is underage.
"We're trying to figure out what these [people] had in mind," an unnamed federal official told 9NEWS.
Sources tell NBC two of the men had tattoos and jewelry popular with white supremacists.
"This is a methamphetamine and firearms case that arose from a traffic stop made by an Aurora Police officer. Firearms and methamphetamine were seized, and a number of individual are in state custody. The matter continues to be under investigation," said U.S. Attorney Troy Eid.
"We're aware of the matter discussed tonight by the Aurora Police Department. Federal law enforcement is working hand-in-glove with the Aurora Police Department. Because this matter is currently under investigation, there is little we can say right now," said Eid. "We can say this: We're absolutely confident there is no credible threat to the candidate, the Democratic National Convention, or the people of Colorado."
Federal officials plan to hold a news conference on Tuesday afternoon.
Officials tell 9Wants to Know the guns, ammunition and scopes were concerning because of the hour of the arrest and the suspect's previous criminal history.
"There is no reason for someone [with a criminal record] to have rifles with scopes," said an unidentified source.
People convicted of a felony are not allowed to possess guns.
Gartrell faces charges of drug possession and possession of materials to make amphetamines.
"Federal agencies are working together to do a follow up investigation after the arrest," said the official. "There may be pending firearms charges."
Those charges will likely be federal charges.
Gartrell has numerous drug-related arrests.
In December 2006, he pleaded guilty to felony possession of a controlled substance and received a deferred sentence.
When Gartrell was pulled over, an Aurora Police sergeant spotted him driving erratically in between lanes near East Hampden Avenue and South Parker Road at 1:30 a.m. on Sunday. He was in a rented 2008 dark blue Dodge ram truck.
Gartrell was driving with a suspended driver's license and Aurora Police say he was on probation for previous drug charges.
"Behavior like this we see as a problem," said Marcus Dudley with the Aurora Police Department. "The vehicle was rented and in someone else's name. There is no known address where we could find him if needed, the ammo, the weapons. All of this clearly gives someone reason for great concern."
Gartrell is a DJ at local clubs in Denver, including the Kazmos Lounge. His friends nicknamed him "Wheels" because he's always on the go. The owner of Kazmos Lounge says Gartrell is anything but a racist and says he can't believe Gartrell is being investigated as a possible white supremacist.
"He's just a total goofball. He's always smiling and making jokes, he's a big talker," said Victor Gomez, Kazmos Lounge owner. "He's not anti-black, absolutely not. He's not in any way shape or form a racist."
Adolf has a very lengthy criminal record. He was wanted on warrants for charges including theft, forgery, possession of a controlled substance, burglary.
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