The stars are sending love to Gary Sinise amid a heartbreaking time. 

After the Forrest Gump actor shared on social media that his 33-year-old son, McCanna "Mac" Sinise died in January after a five-year battle with Chordoma, a rare bone cancer, many of his former costars and friends paid their respects. 

"Oh Gary," Katharine McPhee, who briefly worked with the actor on CSI:NY, commented under his Feb. 27 Instagram post. "I'm so sorry."

Added Alyssa Milano, "I'm so sorry, Gary. I'm praying for your family. And sending you love and strength."

In the post, which featured a photo of Mac as well as his birth year and death year, Gary linked out to a longer statement about his son's final years. 

"We are so sorry Gary," added Law & Order alum Angie Harmon wrote in the comments. "You & your family are deeply loved by so many. We are praying for all of you. Love you so very much."