No one here would be saying any of this shit if it was your little brother, or nephew, or god forbid, child. I did dumb shit when I was a kid, and Id bet most of the people in this thread have done similarly stupid things. Whether or not you learn from the stupid things you do is what is important.
As far as blaming a kids parents ... that's preposterous, no one can be watched 24/7. Im also fairly certain that you at one point disobeyed your parents teachings. You probabaly didn't die because of it. As far as my own property goes ... hell yeah Id be pissed, maybe an ass whoopin was in order, but a death sentence is a little rediculous.
There may be details Im not aware of, maybe the kid pulled a weapon or attacked the guy in which case all the above goes out the window. Outside of that the shooter needs to be dragged out into the street and shot.