He's in love with her. She's still mourning the man she loved and lost.
Bosco was there when Sarah's fiancée was killed. He was there when her world was shattered by the news.
Sarah isn't ready for Bosco, but he's been patient, biding his time until the day she realizes that she's in love with him too. But when illness strikes in the most devastating of places, their worlds are changed forever.
Sarah may not be ready, but Bosco isn't going anywhere. She needs him, whether she wants to admit it or not.