The impact at the station in the 2700 block of SW Trenton Street knocked down a brick pillar and sent a shelf flying into a customer.
"I'm still shaking, I can't believe I'm not dead," said Lidiya Vanvalkenberg. "It was only this far from me and if it hit me I was going to be dead."
Medics checked her out and she's OK. The driver is as well, but investigators still aren't sure what went wrong.
Firefighters briefly evacuated the post office until they decided it was structurally sound. The pickup truck damaged a concrete and brick column and two large windows as it made entry into the lobby.