He could have turned to answer someone behind him;been pushed;stuff happens.
Groundhog Daty Eve I took about two steps out of my car and went down hard on the ice ground;it happened so quickly I barely kept from hitting my face.A few years back ,a friend stepped out from his house and fell on unseen ice,struck his head and needed stitches.
Falls happen quickly and there isn't much to be done while you're falling.
Do it over until you can get it right.