It’s a horrible sick thing on that video, but if you want to report factually, according to the news reports today, the victim did not die. He was interviewed by the police after the incident, but refused to press charges.

I don’t know where you got the information that the onlookers in the dojo included the local police, but if that’s true it might explain why a real investigation apparently didn’t happen. You would think that the police would have been committed him to an institution for treatment (medical injuries and mental health), rather than just saying “He didn’t want to press charges.” That seems quite suspicious to me, but I don’t know what normally happened to homeless mentally disturbed people in that area, back in that day.

Dumfries, VA where this happened is a small town about 20 miles from Washington, DC. It’s very close to the Marine base at Quantico.
It was a “hicksville” back then; the DC metro area has since expanded.

I think this is what happens to mentally ill people when they live in a hick town and bother dangerous people who are even sicker.
It’s sad that these men were Marines. Given the prima facia video, they should have both gone to prison for attempted premeditated murder, assault and battery with a dangerous weapon, and other charges.
And any local police involvement should also have resulted in prison for the officers involved.

Perhaps there will be a federal investigation now, but I seriously doubt that anything at all will happen.