Four people arrested in connection with the robbery of a Broomfield bank Tuesday night are suspected in as many as nine other bank robberies, according to an arrest affidavit.

The suspects, who displayed what looked to bank clerks like a semi-automatic handgun, were found with BB guns in their car.

An FBI spokesman said investigators believe some of the suspects are the "3-2-1 bandits" connected to robberies in Englewood and Aurora and may also have committed two bank robberies in Lafayette, including one earlier Tuesday night.

Those arrested are: Justin Ray Boykin, 26; Audra Boykin, 32; Christy Ann Hull, 28; and Eli Joseph Shortt, 29. The criminal complaint does not specify their towns of residence. Their mug shots were not released because they are being held in a federal facility, and the Justice Department has a policy of not releasing booking photographs.

According to the arrest affidavit made public Wednesday, Audra Boykin entered the TCF Bank, 4100 W. 144th Ave., around 6:35 p.m. Tuesday. She was wearing a black bandanna over her face, a black hoodie and sunglasses. She had what appeared to be a black semi-automatic handgun in her right hand and a white plastic bag in the other, the document said.

Boykin told the tellers, "You know what time it is," and handed the tellers the plastic bag, the affidavit said. Along with $1,418 in cash, the tellers included an electronic tracking device in the bag. Justin Boykin, who was serving as lookout, entered the bank, asked Audra Boykin if she was alright, and then they fled together on foot, according to the affidavit.

Using the tracking device, Broomfield police pulled over a Ford Windstar at Broadlands Lane and Lowell Boulevard. Hull was driving the car, Audra Boykin was in the front passenger seat and Justin Boykin was in the back, the FBI reported. The bag of money was clearly visible on the passenger-side floorboard, the affidavit said. Officers also found two Airsoft pistols under the front seats.

Hull later told investigators she served as a driver in four other bank robberies but did not participate in any of the planning for the robberies. The affidavit said she dropped off the Boykins and Shortt at the Broomfield TCF Bank on Tuesday night.

Audra Boykin told investigators that Shortt used his cell phone to give the Boykins updates on police presence. Shortt denied any involvement, as did Justin Boykin.

Audra Boykin told investigators she participated in nine other robberies in the Denver metro area with Justin Boykin, the affidavit said. According to the document, Audra Boykin told investigators she told Hull where to park, then she and Justin Boykin rode to the bank on bikes. They were trying to find Shortt on Tuesday night when police stopped them.

All four face federal charges of armed bank robbery and aiding and abetting. The charges carry a penalty of up to 25 years in prison.

FBI spokesman Dave Joly said investigators are reviewing pictures and videos from other bank robberies for connections to these suspects. They believe the Boykins may be the "3-2-1 bandits" suspected of robbing the Bellco Credit Union in Englewood and a Bank of the West location in Aurora earlier this month.

Investigators dubbed them the "3-2-1 bandits" because they were heard to say "3-2-1 go" to each other before one of the robberies.

Another TCF Bank at the corner of U.S. 287 and Baseline Road in Lafayette also was robbed Tuesday night around 6 p.m. According to police radio traffic, the suspects in that robbery were a man and a woman with bandannas over their faces. They fled on bicycles, as did the suspects in the robbery of a Lafayette Chase Bank branch earlier this month.

Joly said it's possible the same group carried out those robberies, but investigators are still reviewing the evidence.