"With the blood you lost, you need to get medical help," Ruedi Eggers said.
Eggers said he saw the whole thing.
He says he and his wife were sitting on a bench off the parkway trail with the soon to be victim -- along with a homeless man who had the dog.
"When he tried to get on his bike the dog charged him, and jumped on him, and threw him to the ground.
"You can see there is the first bite right there, and he walked over here, and here the owner was able to get the dog under control.
"In the meantime he got a bite on his upper lip, a bite on his cheek, and a big, big hole in his knee," Eggers said.
Sacramento County park rangers investigated the attack, interviewing Eggers and the victim, but they couldn't give us any more information on camera.
"I feel really bad for him, I hope he's OK -- it's scary," Eggers said.
Pam Viray and her family rode by the scene moments after the attack. She says hearing the story won't keep her away from the popular walking and biking trail.
"I'm pretty cautious, and I'd like to think I could fight off a dog -- maybe? I'd like to think that," Viray said.
(Fox40 - May 7, 2017)