Neither has spoken about the split in detail, but Cooper let slip during a probing interview with DJ Howard Stern on Monday (14Mar11).
The actor told the host, "It was just something that happened. The good thing is, we both realized it... Sometimes you just realize it."
He added, "It just wasn't right... Things happen."
Meanwhile, Cooper denied reports he and girlfriend Renee Zellweger have secretly wed, explaining the wedding ring he has started wearing belonged to his late father.