"Gabriel just felt it wasn't working anymore," the source says. "When they were first together the 9-year age difference between them didn't phase him, she was the most beautiful woman he had ever dated and he was totally in love. But as time went on he started feeling it more and more.
"Also, Gabriel started noticing other women, and being attracted to others, and he felt it just wasn't right to stay with Halle in those circumstances.
"Gabriel is a really nice, decent guy and he would never cheat on her, but I suspect that he had become attracted to someone and that he felt he needed to break it off with Halle before anything developed any further."