Kevin Costner's didn't see his divorce coming, according to source.
Christine Baumgartner filed the papers Monday and the Yellowstone star was said to have been "stunned."
Earlier this week, his rep's released a statement, saying, "It is with great sadness that circumstances beyond his control have transpired which have resulted in Mr. Costner having to participate in a dissolution of marriage action."
They have been married for 18 years and have three children.