There are a lot facts that need to be clarified, but it's difficult to believe it was necessary to kill this young man. What was he doing approaching a vehicle when he was off duty? If this vehicle posed a risk then he should have used more caution and called for backup. His training should have been such that he could have dealt easily with an intoxicated person (or two). Especially if one was under the vehicle. A clean background doesn't mean dick at any time during an investigation, its only mitigating circumstances that are considered in sentencing. Something doesn't sit right here and until all the facts have been laid out, it's impossible to come to any firm conclusion(s). Everything else is sheer speculation.