La shan dra armstrong's sister said the troubled mom acting strangely in the weeks before killing herself and her three children. mara s mara schiavocampo has more. >> reporter: after losing so much, the family is trying to make sense of the senseless and figure out why a 25-year-old mother would kill herself and three of her young children. >> and i'm like, mom, what happened? calm down, calm down. and that's when she told me, she said, she drove the van into the water. they're gone, they're gone. >> reporter: though armstrong, a student and working single mother of four, was overwhelmed at t...