No, he doesn't deserve to be in jail, but make no mistake, he DOES need help.
And, yes, he very well could graduate to people IF he doesn't get help.
Normal kids don't like to just kill things. Not like THAT.
Did you and your fiancee break into a reptile house with the intent to go on a reptile killing spree? Would you have if you were given the opportunity?
I know I don't know you, so I cannot really say, but I highly doubt you would have.
I, too, hold the parent responsible for the child being gone long enough to do damage like that, period.
And I, too, think that the parents should go into therapy of sorts.
I grew up with four brothers, and I can tell you, NONE of them just killed things to just kill things.