As someone who struggled with depression herself, Marie says she can imagine what her son must have been feeling.

"When I had postpartum [depression], I remember vividly driving that car and thinking ... how people would be better off without me," Marie says. "I really believed that."

But something stopped Marie from acting on any suicidal impulses. "It was my age that told me: 'Marie, that's crazy,'" she says. "Children don't have that kind of age behind them. ... When they're 18, everything [seems] hopeless."

Marie says Michael was worried about so many things in his life—things that she says wouldn't seem so big to other people. But one thing Marie can certainly relate to is something her son told her the very last time they spoke. "When I heard him say to me, 'I have no friends,' it brought me back when I went through depression," she says."If I went through that whole experience just to understand my son, that was worth it to me."