The State Employees' Credit Union in the 800 block of North Smithfield Road was robbed around 11 a.m.
The suspect handed a note to the teller indicating he had a gun and demanding that the teller empty the cash draw.
Two suspects, 17-year-old Glenn Bernard Wilkins of Aragon Drive and a 15-year-old boy, were arrested about two hours later at a home on Second Avenue. Police said they found the money inside.
"These arrests happened as quickly as they did because of citizen involvement," said Knightdale Police Chief Jason Godwin. "We received a phone call about a man acting suspiciously near the credit union and were able to respond quickly. I can't thank the people of Knightdale enough for speaking up when something doesn't feel right. In this case, it led to two apprehensions within a couple of hours of the robbery."
Wilkins is facing armed robbery charges, while the 15 year old is charged with being an accessory to the crime.
Wilkins was jailed at the Wake County Detention Center under a $200, 000 secured bond. The other teen was held on a secure custody order.
No employees were injured during the robbery.