Mary Hart on Death of Marie Osmond's Son

Marie Osmond is mourning the death of her 18-year-old son, Michael Blosil.

"Entertainment Tonight's" Mary Hart, a longtime close friend of Osmond's, calls it "one of the most difficult stories that I have had to report in my 28 years" with ET - "because it is so personal."

Blosil was one of Osmond's eight children. Marie adopted five of them, including Blosil.

On "The Early Show" Monday, Hart said she saw Osmond and Blosil only a month ago, in Los Angeles.

"He had struggled," Hart says. "He had been in and out of rehab. And, Marie, always looking for the silver lining, had always hoped for the best. … He was in excellent spirits. I've seen him throughout the years, but on this particular day, he and Marie were so excited about him attending the Fashion Institute of Design and Merchandising in L.A. They were upbeat, and he was very happy, and seemed to be looking toward the future."

Photos: Osmonds' Highs and Lows

With a phone call early Saturday morning, Hart says, she learned the news: Blosil was dead.

Friday evening, after 9 p.m., he succumbed to what Hart says she's told was a battle with severe depression. She says he leapt to his death off the downtown L.A. apartment building where he lived.

Nearly 20 minutes later, at 9:24 p.m., a 911 call was received by the L.A. Fire Department.

According to Hart, a suicide note was found. A source tells Hart that, in it, he wrote that, because of his depressive state, he felt that he had no friends and did not fit in.

Nearly 14 hours later, a grief-stricken Osmond released a statement to ET's Web site saying, "My family and I are devastated and in deep shock by the tragic loss of our dear Michael, and ask that everyone respect out privacy during this difficult time."

Her brother, Donny Osmond, "often her rock," says Hart, told Hart, "Please pray for my sister and her family."

Yesterday afternoon, Hart spoke with a man who said he's Blosil's roommate. "He's probably the funniest, happiest guy I've ever met in my entire life. This is something I would never expect," the man said.

Marie, says Hart, "my dear friend, is finding solace in her faith and her family. And I find tremendous grace in her own words: 'I really believe that it's the lows that make us who we are. It's not the success. It's how we handle all that.'"

Right now, says Hart, Marie is handling everything privately and, although the Osmonds live by the motto, "The show must go on," for Marie, it is just too soon: Donny and Marie's show at the Flamingo Hotel and Casino in Las Vegas has been suspended until further notice.

"You can bet," says Hart, "she has loving arms around her. The Osmonds are a very close-knit family and, in times of loss or tragedy, they support each other and really band together as a family, and in love."