ET has learned that Marie Osmond's son Michael Bryan leapt to his death Friday night in Los Angeles. Contacted by phone this morning, Donny Osmond told us: "Please pray for my sister and her family."

Here are the details: Michael, who was 18 and is one of Marie's eight children, died after jumping from his downtown Los Angeles apartment at about 9 p.m. on Friday night. He left a note explaining he intended to commit suicide due to his life-long battle with severe depression that left him, he said, feeling as if he had no friends and could never fit in.

"My family and I are devastated and in deep shock by the tragic loss of our dear Michael and ask that everyone respect our privacy during this difficult time," Marie, who helped her son fight depression throughout his life, tells ET.

Donny and Marie's Las Vegas show has been cancelled tonight.