Shaughnessy grew up in Jersey City, New Jersey in the 1930s and began playing drums while in his teens. He soon began playing jazz drums in New York City and became a staff musician at CBS in the 1950s. He also became a well-known big band drummer, playing with stars such as Benny Goodman and Tommy Dorsey.
In 1963, Shaughnessy joined the Tonight Show Band, playing drums throughout the show's Johnny Carson years. He played for most of his tenure at the Tonight Show under bandleader Doc Severinsen.
After Jay Leno took over for Carson on the Tonight Show in 1992, Shaughnessy continued teaching drumming privately and at clinics throughout the U.S.
One of Shaughnessy's career highlights was a 1978 drumming "competition" on the Tonight Show against another legendary drummer, Buddy Rich. The moment went on to become one of the Carson-era Tonight Show's most memorable moments: