Alyssa Milano (who once dated Haim): Just woke up to the sad, sad news that Corey Haim passed away. RIP sweet boy.
Ashton Kutcher: Childhood hero
Christina Applegate: My thoughts go out to Corey's family and friends today. So sad.
Ralph Macchio: Always so sad and disturbing when the addiction and demons prevail. RIP Corey Haim.
Khloe Kardashian: So sad! God bless!!!
Lisa Ling: Goodbye Lucus. RIP Corey Haim
Fans also expressed their sadness over the teen star's passing. Among them: "Tragedy takes the stage as the curtain falls prematurely on the kid with the smile and talent that charmed us all. RIP Cory Haim ..." and "ralph macchio, stay stafe. i can't handle another former heartthrob loss today."