Here's the deal -- the 20-year-old internet personality was cruising down a slick Miami highway in his expensive whip Saturday morning while on the platform, Kick ... with the beginning of the now-viral moment showing him looking down at his phone while behind the wheel.

Doherty suddenly loses control of the vehicle, screaming as he smashes into a roadside railing -- and his cameraman in the passenger seat, who was capturing the whole thing, begins to moan in pain after the big hit.

There's a bit of panic heard as the camera gets knocked out -- and the aftermath eventually confirms just how bad the crash was.

His cameraman reportedly had some minor damage, with blood spotted on his face -- outlets claim the 2 were sent to the hospital, with the man behind the camera getting some stitches.

BTW, it seems Doherty has been catching heat ever since Saturday's wreck ... with many online pointing out Jack was more concerned about his McLaren than the dude that was with him.