In what circumstances will a defendant be held liable for assault or assault in a domestic violence case?

In People v. Cravens (2012) 53 Cal.4th 500, defendant and others confronted the victim, and a fight ensued. Defendant's friend fought the victim first, and then all of the men kicked the victim. The victim was able to get up but was unsteady. Defendant "coldcocked" the victim and the victim went immediately unconscious, fell, and his head hit the concrete. (Id. at p. 504-505.) Defendant bragged to friends after the fight that he had "'punched [the victim] out'" and "'put [the victim] to sleep.'" (Id. at p. 506.) The victim died of a skull fracture. (Id. at p. 505.)