Russian Roulette by Anthony Horowitz

The prequel to Alex Rider Series.
Yasha Gregorovitch's parents worked in a fertilizer and pesticide factory. But after an incident, he becomes Yassen Gregorovich. He meets Scorpia and he becomes a killer, hesitant to kill at first, but later gets used to it. He meets Alex Rider's father John Rider who saves his life once. He oves him and never killed Alex Rider, even when he is supposed to.
What made Yasha, a 14 year old boy to Yassen, a grown up person who choses to be a killer? How did he meet Scorpia?How had John Rider saved Yassen's life?
Read this book and find out about Yassen's past!