DENVER -- An early-morning robbery at a west Denver credit union was thwarted when police spotted two men coming out of the building, then running back inside.

Numerous police officers responded to a robbery in progress call at the West Denver Community Credit Union, 3299 W. Alameda Ave., Thursday morning.

According to police, the manager arrived at the credit union and noticed someone sitting on a nearby RTD bus bench.

As she began to open the back door, an armed man jumped over the fence surrounding the adjacent air conditioner. The woman pulled the door shut, then bolted toward her car in the parking lot.

A source told 7NEWS that the manager waved her arms at a bus driving by in an effort to draw attention.

"That's when the man who had been sitting on the bus bench ran over and offered to let her use his cell phone," the source said.

A few seconds later, the fake good samaritan also brandished a gun.

Police say both men ordered the manager into the building and demanded cash.

After grabbing the cash, a dye pack exploded, covering one of the robbers with ink.

Police said they were alerted by both a silent alarm and by a citizen who called and said something didn't look right at the credit union.

The first police officer arriving at the location spotted the pair coming out of the building.

"The duo tried to run out the double front door, but the doors were locked and they bounced off the glass," the source said. "That's when they tried to 'karate kick' the doors. Police arrived when they were on their second try."

The two surrendered without incident.

Police identified the suspects as Paris Peterson, 25, and Markieth Chandler, 27.

Both are being held for investigation of aggravated robbery.

When Airtracker 7 arrived over the location at about 7:25 a.m. one man could be seen on the ground, his hands cuffed behind him. He was escorted to a waiting police car.

"This is a great example of our partnership with the community," said Lt. Matt Murray. "In this case, it was a citizen and her willingness to get involved that solved the crime."

The credit union manager was shaken but not injured.

The business remained closed all day Thursday, and is scheduled to re-open Friday.