Moses struck him with his fist and killed him. He said This is of Satan’s work

1) Did Moses pbuh kill the Coptic by mistake, meaning without the intention to kill him, but it occurred because of a blow? And if Moses’ killing of the Coptic was intentional, does that make it a disobedience to Allah or an unfavored action?
2) The thing described to be {of Satan’s work}, was this the action of the killing (by Moses)?
3) What did Moses pbuh ask forgiveness for? And what is the guilt he committed?