Who killed Jessie Riley in the rot and ruin book?

In "Rot & Ruin" by Jonathan Maberry, Jessie Riley is killed by a group of teenagers known as the "Boys." They are part of a gang that exploits the post-apocalyptic world, showing a violent disregard for life. This event serves as a pivotal moment in the story, highlighting the dangers that exist beyond the Zombies and the moral complexities faced by the characters.