For co-perpetrator liability under section 196A of the Criminal Law (Codification and Reform) Act to be established, the State must prove that accused persons acted in association with common purpose and each had the requisite mens rea, whether by intention, knowledge, or realization of risk. Active association can be implied from strategic positioning, shared planning, and coordinated conduct. The conduct of the actual perpetrator is deemed to be the conduct of every co-perpetrator where common purpose is established, even if not all directly contributed to the criminal act. Culpable homicide rather than murder is the appropriate conviction where, despite use of a lethal weapon causing death, the circumstances (darkness, mistaken belief, lack of identification of victims) negate proof of intention to kill beyond reasonable doubt, leaving only negligence. In sentencing for culpable homicide, the degree of negligence must be properly assessed from the circumstances on the ground, not merely from the fatal result. Trained persons in lawful possession of firearms bear heightened responsibility to apply the principle "if in doubt, do not fire" and sentences must reflect both individual circumstances and the need for general deterrence against unlawful use of lethal force.