The 38-year-old musician was found dead in a room at the Town Plaza Hotel by an employee on 24.05.10 in the band`s hometown of Des Moines, Iowa. No foul play is suspected.
Neil Portnow - President of the Recording Academy, which runs the Grammys - said: "The heavy metal world has lost an immense talent, and Slipknot`s loyal following will ensure he, and his music, are remembered for years to come."
An autopsy was carried out on 25.05.10 to determine the cause of the musician`s death.
Des Moines local rock DJ Andy Hall said: "This is a big blow, not only to the community of Des Moines but fans of metal at large, worldwide. It`s a devastating loss. Paul was a wonderful human being."
Gray is survived by his wife Brenna - who is currently pregnant with their first child.
Heavy metal band Slipknot - who won a Grammy in 2006 for their song `Before I Forget` - are famed for their extreme onstage behaviour and infamous ghoulish masks, as well as referring to each other by numbers rather than names.
Gray - who wore several different masks during his career, but whose most famous headwear was a Halloween styled Pig mask - was known as number two.