Stormbreaker by Anthony Horowitz

They told him his uncle died in an accident. He wasn't wearing his seatbelt, they said. But when fourteen-year-old Alex finds his uncle's windshield riddled with bullet holes, he knows it was no accident. What he doesn't know yet is that his uncle was killed while on a top-secret mission. But he is about to, and once he does, there is no turning back. Finding himself in the middle of terrorists, Alex must outsmart the people who want him dead. The government has given him the technology, but only he can provide the courage. Should he fail, every child in England will be murdered in cold blood.