A witness said the elderly pedestrian waved and shouted at the driver as the bus was making a right-hand turn.
Another witness and others tried to get the bus driver to stop, but he may not have even known he'd hit the man.
VIDEO: Elderly pedestrian struck, killed by SF tour bus
Friends said he was a longtime San Francisco teacher.
San Francisco Deluxe Sightseeing's attorney said the bus driver has not been cited with any wrongdoing.
This accident was devastating for everyone involved. Some witnesses have suggested the victim made it all the way through the crosswalk, but for some reason may have turned back around.
The tour bus company's attorney is hoping that surveillance video from a nearby camera will reveal what actually happened.
Right now, the medical building's security employees said they've been instructed to only release the video to law enforcement.
Roell's friends and friends of the bus driver are devastated. "A very kind spirit and soul and he will be sorely missed," neighbor Cassidy Garvin said.
Garvin and Heather Combs lived in the same house as Roell. "In a way he was family," Garvin said.
"Avid reader, lover of cats, people, teaching," Combs said.
"It's a horrific accident for the bus driver, for the people that had to witness it and especially for the loss of Pieter himself," Garvin said.
San Francisco Deluxe Sightseeing attorney Damien Morozumi said the company has never had a fatal accident before.
Morozumi said he spoke with the bus driver. "He's very distraught and very upset, I think the police had offered him counseling," he said.
Morozumi said some witnesses have reported the driver allowed Roell to fully clear the crosswalk before making a right turn onto post. "For reasons that I don't know or understand, Mr. Roell came back to the bus banged on it a couple of times," he said.
That is when Morozumi said Roell was somehow run over. "We don't understand why he would come back, it's a tragic accident no matter what," he said.
Morozumi said the driver submitted to drug and alcohol tests. According to the California Public Utilities Commission website, San Francisco Deluxe Sightseeing is properly licensed and insured.
This is the third tour bus crash in San Francisco in the last two months. Twenty people were hurt on Nov. 13 when a bus lost control at Union Square. CHP cited the company for mechanical problems and other issues in its fleet.
Then on Dec. 26, nine people were hurt when a tour bus crashed on the Embarcadero. Investigators said another driver cut off the bus.
The victim in Saturday's fatal tour bus accident was an SF public school teacher for yrs. Friends say Pieter Roell taught history/geography— Melanie Woodrow (@MelanieWoodrow) January 18, 2016