The guy should spend time in prison for what he did. You cannot execute someone like he did when they are laying on the ground. Cold blooded murder in my opinion.
He said that he didn’t want the teens to suffer, so he finished them off.
It's curious that often a citizen who goes overboard with use of force appears to be a retired LEO or like that. The movie theater shooter was a retired policeman. This guy appears to be "a retired security engineer for the U.S. Department of State," whatever that might be. Is it because they learned during decades of their service that might makes right, and that shooting of "a civilian" is just a paid vacation?