American media report that the actor died on June 13. According to entertainment site TMZ, Gregory was found dead in his car that day in the US state of Arizona. He reportedly fell asleep and then suffered heat stroke. Gregory's dog Hans was also found dead in the car. It was very hot in Arizona that day.
The exact cause of death is still being investigated.
Gregory appeared in ALF from 1986, a comedy series about an alien who lives in the garage of an American family after an emergency landing. Gregory appeared in all 101 episodes.
He also played a number of smaller roles. He appeared in the children's series Punky Brewster, the sitcom Murphy Brown, the action series The A-Team and an episode of the horror series The Twilight Zone (1985).
After 1993, Gregory retired from acting. He joined the Navy around the year 2000, where he was honorably discharged in 2005. In 2006 he married his childhood sweetheart Sarah.