'Happy Days' alum Erin Moran dead at 56; Ron Howard, Henry Winkler react

April 23 (UPI) -- Erin Moran, who is best known for playing Joanie Cunningham on the classic sitcom Happy Days and its spinoff Joanie Loves Chachi, has died.

CBS News said the Harrison County dispatch in Corydon, Ind., received a 911 call regarding an unresponsive female Saturday afternoon.

First responders who went to the scene determined the 56-year-old actress had died, TMZ said.

An autopsy will be performed to determine the time and cause of her death.

"OH Erin... now you will finally have the peace you wanted so badly here on earth ...Rest In It serenely now.. too soon," her former co-star Henry Winkler tweeted.

"Such sad sad news. RIP Erin. I'll always choose to remember you on our show making scenes better, getting laughs and lighting up tv screens," her one-time Happy Days cast mate Ron Howard -- now an acclaimed filmmaker -- said in his own Twitter post.

Set in the 1950s and '60s, Happy Days ran for 11 seasons 1974-84. It was created by writer-director-producer Garry Marshall, who died last year.