“I am so sad and so grateful for all the times she made me laugh,” said Ted Danson, who starred with Alley in the classic sitcom.
Richards' publicist said a driver opened fire on the pair after passing their vehicle in Los Angeles.
Actress and model Denise Richards joins Marc on set to talk about parenting and adoption.
The former celebrity couple broke up in 2005 while the "Wild Things" actor was pregnant with their second child.
"You were right," Richards posted to fans on Instagram. "I thank all of you who sent me messages."
The actress recalled how she still kept the holiday spirit on "The Real Housewives of Beverly Hills."
This is the second reality show for the actress, who starred in two seasons of "Denise Richards: It's Complicated."
"It’s difficult, but far from impossible and we smile more than we cry.” -- Regina King