He tweeted Sunday afternoon, "2day the world lost a little piece of sunshine. My deepest condolences go out 2 Brittany's family, her husband, her amazing mother Sharon."
The actor adds, "see you on the other side kid."
Kutcher, 31, and Murphy, 32, costarred in the 2003 comedy Just Married, and were romantically involved off screen.
- Feb. 12, 2017 The cutest kiddos of the 2017 Grammy Awards