SAN FRANCISCO -- A window washer fell screaming 11 stories from a bank building Friday morning onto a moving car, crushing its roof and sending shattered glass flying into the street, police and witnesses said.

The window washer, who was not immediately identified, suffered critical injuries, but he was conscious, police said. He was taken to San Francisco General Hospital.

Police look over a car that has a caved in roof after a window washer fell at least 11 stories onto a moving vehicle in San Francisco, Friday, Nov. 21, 2014. AP Photo/Michael Liedtke

Witnesses described seeing a falling blue streak and the man's shadow as he fell down and then hearing a crashing sound as he hit the car and then rolled onto the ground.

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"As he was coming down, he was definitely screaming," said Bianca Bahman, 31, a pre-medical student at San Francisco State University who was on her way to the gym and was on the corner where the man fell. "It all happened so quickly. It was so instantaneous."

The man was moving equipment on the roof of a bank building in the heart of San Francisco's financial district and not on a window-washing platform when he fell, San Francisco police Sgt. Danielle Newman said. The platform was on the ground at the side of the building, and cables were hanging from its sides.

Sam Hartwell, an eyewitness, told KCBS in San Francisco that he was crossing the intersection when the accident happened.

"I was actually looking in the direction of where the fellow fell off the building and I saw something blue out of the corner of my eye falling and then I heard the loud thud and the shattering of the back of the car," Hartwell said.

Once he realized it was a falling body, he said about 20 people rushed around the man, at which point calls were made out to 911. Citizens then started to direct traffic.

"Everyone did the right thing, we didn't disrupt the integrity of the spinal cord. We covered him with clothing. He was obviously in shock," Hartwell said.

Hartwell went on to describe the victim's condition in great detail and said he was frothing at the mouth while he appeared to be lucid in one eye. Blood could be seen coming from his ears, he said.

"He understood what was going on. We spoke to him in reassuring terms. I hope he's going to be okay," he said.

No one else was injured, including the driver of the green Toyota Camry the man fell on. The driver did not want to comment, Newman said.

Blood, glass and one shoe were in the street as onlookers stood behind yellow police tape and watched officers work.

Recent incidents involving window washers show the dangers of the job.

Last week, the collapse of a World Trade Center scaffold left two window washers dangling from the nation's tallest skyscraper. The workers were trapped 68 stories above the street when a cable suddenly developed slack on Nov. 12.

The workers held on to the teetering platform for two agonizing hours. One called his wife during the ordeal, fearful that it might be his last opportunity to speak to her. Firefighters used diamond cutters to saw through a double-layered window and pulled the men to safety. They were not injured.

Last month in Irvine, California, two window washers stuck for hours near the top of a 19-story high-rise were pulled to safety by members of a search-and-rescue team.

It was unclear how the workers became stuck on the side of the office building near the San Diego Freeway. Neither worker was injured, authorities said.

Also last month in downtown Oakland, California, two window washers were stranded outside the 19th floor of a high-rise for nearly two hours before employees inside realized they were in trouble and called for help. They also were not injured.