But the 35-year-old, whose real name is Adam Grandmaison, said he quickly realized it was no joke.
"It was just pure shock," he told Inside Edition of the moment, which was caught on video.
Viewers got a big surprise during the "No Jumper" podcast when a hand pointing a gun suddenly entered the frame on Sunday night. In the video, Grandmaison tries to push away the weapon. "Give me all your f***ing money," a voice says as the YouTuber appears to laugh, seemingly not sure if it is a prank.
"The 'hee hee' that I let out is just this bizarre nervous reaction, I guess, because at that moment I couldn't imagine that this was seriously happening," Grandmaison explained.
Grandmaison's staff fought off the man, who can later be seen on the ground in the video, with one of Grandmaison's staff apparently kicking him.
But some fans are questioning whether the attack was fake.
"Completely setup," wrote one commenter online. "It was staged!"
Grandmaison has a message for the doubters. "It was definitely a real robbery," he said.
David Tran, 24, was arrested at the Melrose Avenue studio where Grandmaison livestreams his show, authorities said. The gun was later determined to be a movie prop, according to LAPD spokesman Officer Greg Kraft.
Tran is being held in lieu of $50,000 bail at Los Angeles County Jail, according to online records. He has not yet entered a plea to a charge of attempted robbery.
Grandmaison is credited with helping the careers of rappers including XXXTentacion and Lil Yachty. But he has faced criticism for making videos of BMX stunt riders using homeless people on Skid Row as props, as well as accusations of sexual misconduct, which he denies.