The story here and the one earlier (before his death was confirmed)
https://www.sfgate.com/bayarea/article/bay-area-coaching-legend-shot-campus-21171874.php
are incredibly lacking in details about how and why he was shot.
More questions than answers.
Condolences to the family of this man who apparently was well loved by many.
Considering it was less than 24 yours ago, it's safe to say that your "why" won't come out until a full investigation is completed.
As to your "how", I'm going out on a limb here and say it was likely a firearm.....I know, that's a stretch.
one shot to the head.
The shooter has to be about 28 or 29, estranged from family with two married parents and a brother.