I would try some simple conversation first. And i stress that there are myriad other options than calling the cops or executing a neighbor.
In this case the guy is obviously testosterone driven, so a friendly stop by in the driveway to "Admire" his cars and get to know him will probably get him to stop "showing off" to the porsche guy.
That's how i'd handle it. If that didn't work, then i'd shoot him. (winking at moneyguy
)