The FedEx truck was reported stolen around 1:15 p.m. at the intersection of Ridge Avenue and Lehigh Avenue.
Police managed to spot the truck and pursued it until the truck crashed at the intersection of 25th and Willard streets, becoming wedged between a utility pole and a fence.
A witness, James McCord, saw the crash. He and his son jumped into action.
"He was kind of in disarray because he hit the pole kind of hard. When we got there he wasn't in the best running condition, he was shook up. We ran and chased him down, beat him down," said McCord.
After McCord and his son roughed up the suspect, police say he ran into a vacant home in the 3100 block of Stillman.
Once he emerged from the basement he was placed under arrest.
In recent days there has been a rash of robberies involving mail carriers in the city.
McCord said he was aware of that and felt he had to do something when the FedEx truck crashed on his block.
"I was upset because a lot of post offices have been robbed and now the FedEx guy. It's Christmastime and a lot of robberies are going on with the mail and FedEx," he said.
Police are investigating.