Law enforcement sources tell TMZ ... Balducci was found unresponsive in his bed Saturday. He was last seen around 2 AM that morning and they found him on his right side of his bed later that evening around 9 PM. Paramedics responded, but pronounced Charlie dead at the scene.

We spoke to Charlie's mom who tells us Balducci passed away unexpectedly since he didn't exhibit any kind of sickness. She said the last words he spoke to her were that he's happy to have his boys, who are 17 and 19, respectively.

Balducci was a trailblazer of sorts as a pioneer of reality TV. In 2001, Balducci allowed MTV cameras to follow him 4 months before getting married to Sabrina ... resulting in one of the most infamous rants ever caught on TV.

On the day he was set to get married, the limo driver was running late, prompting Balducci to threaten the limo driver, "I will gut you like the piece of s**t you are" and "I'll hunt you down like cattle."

Charlie and Sabrina were one of 3 couples featured on the reality show "True Life: I'm Getting Married." They were discovered during a dress fitting after Sabrina said a woman came up to them saying they were hysterical. And when the opportunity to appear on the show came up, Balducci jumped all over it.

Charlie and Sabrina were married for over a decade and had two children together.

He was 44.