A viral video showing the beating of a 13-year-old white boy by three African-American youths in Florida has left hundreds of thousands of viewers horrified, but critics say the case doesn't seem to be attracting much sympathy from self-styled civil rights activists.

In the chilling video, three 15-year-old boys repeatedly beat and kick a victim police said was left with a broken arm and two black eyes. 

Although Florida came under fire in the wake of the Trayvon Martin shooting and George Zimmerman's acquittal by activists Al Sharpton and Jesse Jackson - who called it an "apartheid state" - neither has spoken publicly about the bus incident. But one reason the case has not become as racially charged as other attacks may be that many news outlets have either not shown the first few seconds, before the victim goes down behind a seat, and others blur out his face to the point his race is no longer apparent.

The bus driver, 64-year-old John Moody, can be heard frantically calling a radio dispatcher for help, although he was criticized in some quarters for not physically intervening.

"No, you've got to get somebody here quick, quick, quick," Moody pleads on his phone as the assailants take turns landing windmill punches and vicious kicks on the cowering victim. "They about to beat this boy to death over here."

The attack took place July 9 in the St. Petersburg-area community of Gulfport. But the horrific cell phone and surveillance video only came out only recently. Police say the three youths, all African-American, attacked the boy after he told officials at their dropout prevention school that one of them had tried to sell him marijuana.

Most of the focus has so far been on Moody, who retired two weeks after the incident. Moody went on CNN earlier this week to defend himself.

"Me jumping in the middle of that fight with three boys, it would have been more dangerous for other students on the bus for as myself," he told Morgan. "There's just no telling what might have happened."

Moody stopped the bus, and police said the suspects used the emergency exit of the bus to escape. Joshua Reddin, Julian McKnight, and Lloyd Khemradj, all 15 years old, were arrested a short time later. All three were charged with aggravated battery and have since been released. Reddin is also charged with unarmed robbery.

Pinellas County school policy does not require a driver to intervene and prosecutors have said Moody will not face charges, but Gulfport Police Chief Robert Vincent told WFLA that Moody should have stepped in.

"There was clearly an opportunity for him to intervene and or check on the welfare of the children or the child in this case, and he didn't make any effort to do so," Vincent said.