He was shot from behind. That security detail either screwed up colossally, or it was an inside job. I can’t imagine any detail ever letting someone getting behind them so, I think we know which one it is.
TURNS OUT THAT SHINZO ABE WAS ADVOCATING FOR DEFENDING THE TAIWANESE FROM AN INVASION FROM THE CHINESE. THIS WAS A HIT JOB BY THE RUTHLESS CCP, PLUS SHINZO'S SECURITY DIDN'T EVEN BOTHER HELPING HIM, THEY WERE PAID OFF.