Dec. 15 (UPI) -- Celebrities took to social media Sunday night to express their horror and sadness at the stabbing deaths of beloved 78-year-old actor and filmmaker Rob Reiner and his wife Michele in their Los Angeles home.

The double homicide is under investigation by the Los Angeles Police Department and no arrests have been announced yet.

"Rob Reiner co-starred in one of the most influential sitcoms of all time, had an incredible run as a director -- and was one of the kindest and most considerate human beings I've ever met in this business. RIP to Rob and to Michele," film critic Richard Roeper said, referring to Reiner's break into acting on the classic TV series, All in the Family.

"Rob was my true hero. A true visionary titan and a lovely lovely person. One never knows if it's proper to post during something as tragic as this. But I just want the world to know what so many of us know in the industry. Rob was the best," filmmaker Paul Feig said.

"Please God shine some light on this world. Not Rob Reiner. Not so tragically," actor Rob Morrow said.