Who is Miro Shantas from After the First Death and what is their importance?

Miro Shantas is a teenager who thinks he is about sixteen, but he is unsure of his real age . Miro was born in a Middle Eastern country where he and his brother were left alone after the reported deaths of their parents. Miro and his brother lived on the streets, often stealing or begging for what little food they were able to get. Then one day they were approached on the street by a stranger who took them to a refugee camp where they were put through a school teaching them to be terrorists. Miro and his brother came to America with this stranger who was now their leader. Miro's brother died in a terrorist attack.
Miro is one of the hijackers who hijack a bus filled with four- and five-year-old children on their way to a summer day camp. Miro's job is to kill the bus driver, an act that will finally make him a man in the eyes of his fellow terrorists.