I'm sobbing stop.

I think it might be related to his blind eye.

They did confirm it was an "accident" , to my guess it was an accident related to his sight, having one eye which can barely see do make blind spots(more than normal)

And I'm guessing it was an accident while he was "Jekyll" with clear eyesight. Which probably made "Hyde" blame himself even more. Because it might've been avoided if he didn't need to hide the fact that he couldn't see from one eye...