'Welcome Back, Kotter' star Horshack dead at 63

Ron Palillo, best known for playing Arnold Dingfelder Lutz Horshack in '70s sitcom "Welcome Back, Kotter," has died at the age of 63. His agent, Scott Stander, confirmed Palillo died of a heart attack in Palm Beach Gardens, Florida.

Horshack was known for his signature laugh and his "Oooo, oooo" calls to teacher Gabe Kotter (Gabe Kaplan) on the show that ran from 1975-79 and kick-started the career of John Travolta. Palillo's fellow "sweathog," Robert Hegyes (who played Juan Epstein), passed away in January.

Palillo never replicatd his '70s fame, but was active in Florida theater and taught at G-Star School of the Arts charter school.

TMZ reports that Palillo was found by his longtime partner, Joseph Gramm.