The injured man, 37, extricated himself from one of three vehicles that caught fire and was taken to Harborview Medical Center in critical condition with burns over 50% of his body, said the spokesman, Kyle Moore.
A woman inside a second car was not injured; a man inside a third vehicle -- a pickup truck -- had left the scene and was being sought by authorities, Moore said. "We want to talk to him just to make sure he's OK," he said.
Moore said that he didn't know what led to the crash, but that it did not appear that any buildings were struck by the leased helicopter, which was destroyed. "What we have left is basically just a part of the tail and burnt-out metal from the main chassis of the helicopter," he said.
The crash occurred on Broad Street, near the city landmark, he said.
Arriving firefighters found lines of blazing fuel in the street and thick, black smoke covering the area, with "wreckage strewn across the lawn along with wreckage across the street," he said.
CNN affiliate KOMO said the helicopter crashed near its offices. It was used by CNN affiliates KOMO and KING, according to KING's website.
Rich Marriott, a meteorologist for KING, said weather did not appear to have contributed to the crash -- visibility was clear and winds were calm, he said.
The incident occurred around 7:40 a.m., more than two hours before the Space Needle was to open but at a time when the area was abuzz with commuters en route to work. The Bill & Melinda Gates Foundation offices are about a quarter-mile away.
Representatives of the National Transportation Safety Board and the Federal Aviation Administration were expected to help investigate the crash.