Pappalardo has owned his legally registered AR-15 for 30 years and is a staunch supporter of the Second Amendment.
The AR-15, he says, is "really fun to shoot".
"I mean think about it, is the right to own this gun more important than someone's life?"
"In the back of my head I say, 'What if whoever buys this weapon, their child gets hold of it and brings it to school one day and shoots a bunch of people?' Could I live with that?" The post has been shared more than 320,000 times.
But experts say that after each shooting the AR-15 flies off store shelves amid fears it is about to be banned.
Pappalardo says he supports American's rights to bear arms, but says that deadly assault rifles should not be in the hands of citizens and should be reserved for militray forces only.
"I'm gonna give you a newsflash", Pappalardo said.
"This weapon will never be able to take a life".
"That's five years ago now... so I guess my words were just empty words". Is that right more important?' "Any legal gun owner is capable of snapping and committing a horrific crime even without mental illness", he said.
Pappalardo then places the rifle under a power saw and cuts it in half, before returning to his chair to end the video.
He acknowledged that there are many factors that can be blamed for school shootings but ultimately, he said it comes down to the weapon he was holding in his lap.
Hollywood star Julianne Moore praised Mr Pappalardo's video, tweeting: Please watch this eloquent gun owner explain why he destroyed his gun.
Meanwhile, a high school headteacher in Missouri has apologised for promoting raffle tickets for AR-15 rifles hours after the Florida massacre.