The truck driver was injured as he jumped from the back of the truck.
Police and emergency personnel responded to the scene, in the 2600 block of East Ward Street, at about noon after receiving a report of multiple vehicles struck.
Witnesses told police the truck driver was loading donated goods into the back of the 24-foot truck, owned by St. Vincent de Paul, when it suddenly started rolling down the sloping street.
They said it appeared that the 24-foot truck's brakes failed. The truck slammed into five parked cars as it hurtled down the street.
A silver Toyota at the top of 26th Avenue East had rear passenger side fender damage as it was clipped by the truck. A gray BMW and red SUV sustained more serious damage as the truck plowed into them, pushing the BMW into a garage door and the SUV into a tree.
The truck finally came to a stop as it slammed into a green Toyota Prius and a dark BMW at the bottom of the hill. The Prius sustained the worst damage as its front end was crushed under the truck.
One side of the truck was also ripped away during the series of collisions.
Seattle Fire spokeswoman Lt. Sue Stangl says the driver was taken to a local hospital with an ankle injury.
No other injuries were reported.