Kanye West's behavior has concerned many -- including many of his celeb pals.

On Tuesday, his friend John Legend did an interview with CBS This Morning and revealed that he was with Kim Kardashian in New York City right before the rapper was taken to UCLA Medical Center late Monday -- and he was worried about what was going down.

John said, "We were with Kim actually, you know, right before all of that."

The singer added, "I was concerned by what I saw, so hopefully he's getting some rest and some time to figure things out."

Kim was in the Big Apple to attend the Angel Ball in honor of her late father. After news broke, she skipped the charity bash and immediately flew back to L.A. to attend to her husband.

Legend and West met in 2001. The crooner was hired to sing the hooks on some of West's tracks and later signed to West's label.