EMBED >More News Videos Cellphone video shows the aftermath of a hit-and-run in which a 14-year-old on a bike in Oakland was struck by a car and dragged four blocks.

OAKLAND, Calif. (KGO) -- Graphic cellphone video shows the aftermath of a hit-and-run in which a 14-year-old on a bike in Oakland was struck by a car and dragged four blocks.Witnesses say they saw the car hit the boy on 35th Avenue near the Fruitvale BART station. Officials say the boy was underneath the vehicle and the driver made several turns before stopping the car just before 12:30 p.m. on Wednesday.The video was shot and shared with ABC7 News by Charles Green, who was taking a walk during lunchtime on Wednesday and happened upon the horrifying scene."By the time I got to them, they were switching up, they were both out of the car. She was walking around this way and he was walking around that way. That's where I started," he said.In the video you can hear the boy asking, "Why is no one calling an ambulance?" And at the end of the video you can hear him cry out, "Please, call an ambulance!"Green tells ABC7 News, "I didn't realize what was going on, I had no idea. Even if you look at the video the guy's like, 'Call an ambulance.' And I'm like, what? I didn't know. I thought it was some drunk, didn't know."When asked if the two people he came upon were aware they hit the boy, Green said, "Oh yeah! They were trying to get away. They wanted to get away, they wanted to go."The teen is now in critical condition, with major injuries to his head, torso and legs.Police are urging the driver to come forward."Accidents happen," said Officer Johanna Watson. "We understand that there is panic, that there is often not sure what to do in a critical situation. Do the right thing -- turn yourself in."