Officials search for a motive after a lone shooter sprayed bullets into a church at Annunciation Catholic Church School, killing two children and injuring at least 17 others, mostly children; ABC News' Rebecca Jarvis spoke with Patrick Scallen who ran into Annunciation Catholic Church School during the mass shooting to help the victims; Author Suleika Jaouad opens up about living with cancer; and more on ABC's Good Morning America.

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