Steve Stenberg was in math class when he and others heard the crash at around 2:30 p.m.
"We heard this huge screeching, and a really huge smash and everyone in my math class ran outside," Stenberg said. "There was an old truck that had gone through the chain link fence and hit a fire hydrant."
He said the truck then hit an older iron fence.
"It was smoking inside. I wasn't really sure at the time but I was concerned for their safety and I just wanted to get them out. I was worried there might be a fire or an explosion and I just wanted to get them out," Stenberg said. "I ran and jumped the fence and got the man out."
He said he passed the man to Nick Riddell, another student from the math class. When he tried to help the female passenger, Stenberg ran into a problem - a scared and angry dog.
"I was reaching to unbuckle the lady's seatbelt and it was biting my hand," he explained. "The lady told me to get the dog first."
Stenberg did as he was told, chasing the snapping dog through shin-high water. He finally caught it and locked it in the back of a nearby truck.
He said he was bitten several times, but added, "I couldn't really feel it at the time, because there was so much adrenaline."
By then, police and fire personnel were on the scene.
"Officers found the driver sitting down outside the car," said Pleasanton police Sgt. Bob Leong. He said firefighters extricated the woman.
Stenberg said neither of the two appeared to be seriously injured.
"The man, for sure he had a concussion. He was out of it. The lady, she could talk but she was bleeding from her eye; she had cuts all over the place," he said.