The 55-year-old was tragically hit by a vehicle while he was crossing a busy street in Virginia Beach on July 14 ... and in 911 recording of the incident, obtained by TMZ Sports, you can hear a woman rallying pedestrians to try to help Whitaker.

The woman says she didn't know Whitaker -- but saw he desperately needed help and vowed to do everything in her power to try and save him.

In the audio, you can hear the woman describe the dire scene, saying, "He is on the ground right now ... I'm not sure if he is alive."

But, when dispatch asks the woman if she's willing to administer CPR ... she doesn't think twice -- and tries to get others at the scene to help her.

"He's not alive. Okay, we have to roll him over," she says in the recording. "I want to do it!"

You can hear in the audio ... the woman and others try to get Whitaker on his back -- but the scene the woman paints is grisly.

"Oh, there's a lot of blood!" she says, while another man in the audio adds, "There's a whole bunch of f**king blood!"

Even still, the woman presses forward, saying, "Okay, let's do it. Come on! Let's just try it! If there's any way we can help him!"

Despite heroic efforts, the pedestrians were unable to save Whitaker ... and after emergency medical officials arrived, they pronounced the former boxer dead at the scene.

The tragedy hit the boxing world deeply, with Floyd Mayweather paying tribute to Pernell on social media saying, "R I P champ, one of the best fighters to ever do it."