PHOENIX -- A newly released 911 tape obtained by CBS 5 News describe a vicious dog attack that left a park worker seriously injured.

UNCUT: 911 Call. Some listeners may find parts of the call disturbing.

The tape shows how an alert passer-by with a cell phone managed to guide police to the scene of the attack near 35th and Northern avenues.

The pit bulls ripped off Carol Corona's clothing and severely bit him as they dragged him through the grass, police said.

The 911 caller told the dispatcher he thought the man was dead. It turned out Corona was not dead.

"These dogs are tearing him up," the caller said.

Over and over the 911 operator can be heard asking what was going on.

"Are other people trying to scare the dogs off?" the dispatcher asked.

"Yeah, there's this cab driver trying to scare the dogs off," the caller said.

The caller appeared frustrated because he was unable to help Corona. "I don't have my gun or I'd shoot the dogs right now," the caller said. "They have his arm shredded."

Four minutes after the man called for help, police arrived. They shot and killed the two dogs.

The dogs apparently escaped from a nearby yard.

Corona was rushed to the hospital with serious bites to the upper part of his body.