grandma getknocked down, and she hits the floor, and then you see the back tire go over something. amy: you know, i was probably screaming and crying, and then we walk into a room with like 15 doctors. you think it's maybe a dream or something, a nightmare. hsi-pei: i mean, it was a lot to take in, thinking your daughter was safe with grandma at her house, expecting to go see her for dinner and having the rest of the family being there, to all of a sudden your daughter doesn't exist anymore. narrator: after hsi-pei and amy lost their daughter allisoson, they decidided they had to doo something. hsi-pei: i think for me, a lot of it is trying to understand what happened, how could it happen, and find meaning behind it, how to prevent this from happening. we still have a son. we lateter had another child. s, there's--you know, there's just meaning behind this from preventing it from happening ever again for our family. amy: i'm sorry. all: safe streets! narrator: they helped found an effective campaigning group, families for safe streets in new york. amy: basically it's a group that y