(CNN) -- Paul Walker's sudden death has left many in Hollywood nearly too stunned to speak.
As the news of his death spread on Saturday, some celebrities, including Lady Gaga and Alyssa Milano, tweeted their disbelief.
gipson is this true? If so that is incredibly tragic. Praying for his family, friends, and fans. Wow. speechless
— Lady Gaga (@ladygaga) December 1, 2013
这是真的么?如果是真的的话，这真是一个难以置信的悲剧。为他的家人，朋友，粉丝们祈祷。真是让我说不出话了。— Lady Gaga
Adored for his work in the "Fast & Furious" movie franchise, Walker was in the midst of filming a seventh installment at the time of his death.
Two of his co-stars in the blockbuster series, Ludacris and Tyrese, expressed their grief on social media.
"I can't believe I'm writing this," singer/actor Tyrese shared on Instagram, along with a photo of himself with the late star. " My heart hurts it's broken no one can convince me that this is real.... Prayer warriors please pray real hard for his only child, his daughter and family..."