It's alarming video of a school bus attack in Florida. Three 15-year-old students pummel a 13- year-old who tries to take cover from the punches and kicks.

The 64-year-old bus driver calls for help but does nothing else to stop this violent attack. The attack took place July 9 in Pinellas County, Florida. But the horrific cellphone video -- and the surveillance video -- came out only recently. As the boy is pummeled, the bus driver, John Moody, yells at the assailants to leave the boy alone. He also asks dispatchers to send help.

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"You gotta get somebody here quick, quick, quick, quick," he says. "They're about to beat this boy to death over here." Prosecutors say they have no grounds on which to bring charges. "It wasn't like he was looking out the window cleaning his fingernails or something like that," said Chief Assistant State Attorney Bruce Bartlett, according to CNN affiliate WFLA.

According to Pinellas County school policy, the bus driver isn't required to intervene, only to call dispatch. He can step in, if he feels it's safe.

The driver followed his school's protocol but a lot of parents disagree with that policy. Monica Friant is a mom who told Local 4, "He is the adult on the bus. She's the adult on the bus. It's their responsibility to intervene and keep children safe."

Local 4 checked with several school districts in metro Detroit. They all have different policies on how to deal with fights on a school bus.

Watch: Teenagers pummel student on Florida school bus

Most districts require bus drivers to give a verbal warning and call for help. Some require the drivers to step in physically if necessary to stop an attack like the one in Florida.

"Bus drivers should worry about driving the bus and I think that there should be an aide or one of the parents or somebody on the school bus to protect the kids," said dad Jason Hoffman.