What event made Beah decide to leave Sierra Leone forever?

The loss of Uncle Tommy marks the moment Beah decides he must leave Sierra Leone for good. He knows he cannot care for his family, and he is afraid he will end up in the military, committing the atrocities he has been redeemed from, all over again. Only Laura Simms offers him a lifeline: a new home in New York City, far from the violence and political upheaval of his homeland.