Barring a time machine, we've very little way to know when it comes to one specific incident. Again, people distracted by their cell phones kill people on a very regular basis in vehicles without autopilot.
If we had better aggregate stats we could compute the statistical likelihood of it, but this stuff isn't tracked anywhere near as closely or completely as, say, aircraft accidents. I don't trust Tesla's self-reported cherry-picked stats.
People look at their phones while driving with and without autopilot.