cassie was in car picking up brynn 's son for preschool in tenino , washington , when she accidentally ran over brynn 's younger daughter , 17-month-old rowyn , who was killed .
incredibly though , brynn forgave cassie for what happened , acknowledging what happened as a horrific accident .
rowyn was only 17-months-old when she was killed instantly in driveway of her home in tenino , washington , in september last year .