Well, let's see.
He can't outrun me, and he's even slower on the trike.
He hasn't the physical ability to harm me or successfully use a weapon against me, so I can safely reclaim my property.
In addition, he does not fully understand property rights and the concept of theft, so he is not aware of, and therefore, not committing, a crime.
He is, however, a victim because he is unsupervised, so it would be necessary to take him into custody for his own safety, and immediately notify the police and CPS.
I might shoot the bull with him about Tonka trucks, but that's about all.
Sorry to disappoint.
About what I expected. Even though he might grow up to kill someone later, you have your limits. It apparently is somewhere between four and eleven years old for the thief in order for you to shoot them.
LOL, nice...