According to the neighbors who spotted him and chased him off, he's likely neglected and allowed way too much unsupervised time. From the sounds of it, he's disturbingly young, alone a lot, has no friends, doesn't have a dad, and spends all of his time riding around on his bike... and murdering my baby birds in broad daylight. I'm not sure how old this kid is, only that he can jump a fence, ride a bike and murder several baby birds and beat a miniature turkey tom in quick succession.
Killing animals like this is actually a warning sign of a future serial killer. It does stand to reason that if you lack compassion for a terrified, fuzzy duckling and even enjoy torturing them, you could probably kill a person pretty easily.