Let's say in a case where the son bemayzid (+hasro'o) hits his father (chaburo) in a place which shouldn't kill the father, but he still dies from the injury a day later.
Hitting (chabura) his father is chenek, and killing is hereg/sayef.
Standard hereg is a tougher meesa than chennek, except according r' shimon.
Would we say in this case if the meesa of killing his father is worse, that since the part that killed his father, was done beshoygayg, does he go to golus, and it paturs the hitting/chabura part?
Ps: the fact that the father dies later, doesn't place it in a chronological later phase, concerning the punishment.
The sons act was one, and one act only that happened at one and the same moment.