Officials said the the SUV was on Wall Street when the truck came speeding out of an alley near 3rd Avenue just before 6 a.m.
The impact sent the vehicles crashing up onto the sidewalk and into the wall of the nearby apartment building.
"I opened the door and saw car parts everywhere," said Ricky Walker who lives in the building.
Three people who were in the truck suffered critical injuries and had to be cut out of the mangled wreck. They were rushed to Harborview Medical Center.
The driver of the SUV was less seriously hurt.
Seattle police officials said an officer tried to pull the truck over prior to the crash, but the driver refused to stop. The officer followed the car, but turned off his lights and stopped following the truck about two minutes before the collision.
Officials said there was no pursuit under way at the time of the crash, and it was not immediately clear why the truck driver refused to stop for the officer.
However, late Tuesday, detectives said they learned the truck had been stolen. The truck's owner called police about an hour after the crash to report his truck had been stolen at some point overnight.