Youtube's Grant Thompson Shown Paramotoring Months Before Death

Grant Thompson, creator of YouTube's popular "King of Random" series, died doing an extreme sport he loved and mastered -- based on this video -- even though he'd just picked it up a few months ago.

TMZ's learned Grant Thompson was paramotoring -- it's also called powered paragliding -- when he died Monday night in Utah. In this video shot in March ... Thompson's seen handily operating a paramotor to fly all around and high above an open field.

At one point he pulled off a maneuver his friend calls "so risky" as he recorded the flight.

Law enforcement confirmed a paramotor was involved in Grant's accident.

His brother, Mark, tells us Grant took up the sport about 5 months ago and says it was his new obsession. We're told the footage seen here was taken at the same spot near his home where he was supposed to land ... had he made it back from the flight that killed him.

We broke the story ... authorities found Grant's body Tuesday. The Washington County Sheriff's Office got a call about an overdue paraglider who'd gone off radar near a state park, and they quickly launched a massive search.

Along with Grant's paramotoring gear, a video recording device was found at the crash site and is being reviewed to determine the cause of the accident.

Grant started his YouTube channel in 2010 and amassed more than 11 millions subscribers while documenting experiments, life hacks and random weekend projects.