As it happened, this was a violent ex-husband who had made the poor woman live in fear of her life for some time. He was threatening people who tried to intervene, so the driver decided to use his car as a last resort - the reports say he drove slowly towards the knife man, he didn't drive full-speed at him.
Yes, it's manslaughter, but the extenuating factors mean that as far as I'm concerned, he shouldn't be charged. I doubt if a jury would find him guilty, although he has killed a man.
(edit - and there were many eye-witnesses, who have reported that the knife man was under the car calling out for help, but no-one was minded to assist).