are two persons, the father and the son, go out a-hunting.  They take different roads.  The father hears a rushing among the bushes, takes it to be game, fires, and kills his son, through a mistake.  Here is innocent blood shed, but yet nobody will say the father ought to die for it.  So that the general rule of law is, that whenever one person has a right to do an act, and that act, by any accident takes away the life of another, it is excusable.  It bears the same regard to the innocent as to the guilty.  If two men are together, and attack me, and I have a right to kill them, I strike at them, and by mistake strike a third and kill him, as I had a right to kill the first, my killing the other will be excusable, as it happened by accident.  If I, in the heat of passion, aim a blow at the person who has assaulted me, and aiming at him I kill another person, it is but manslaughter.

(Foster. 261. section 3):  “If an action unlawful in itself is done deliberately, and with intention of mischief, or great bodily harm to particulars, or of mischief indiscriminately, fall it where it may, and death ensues, against or beside the original intention of the party, it will be murder.  But if such mischievous intention doth not appear, which is matter of fact, and to be collected from circumstances, and the act was done heedlessly and inconsiderately, it will be manslaughter, not accidental death; because the act upon which death ensued was unlawful.”

Suppose, in this case, the mulatto man was the person who made the assault; suppose he was concerned in the unlawful assembly, and this party of soldiers, endeavoring to defend themselves against him, happened to kill another person, who was innocent—­though the soldiers had no reason, that we know of, to think any person there, at least of that number who were crowding about them, innocent; they might, naturally enough, presume all to be guilty of the riot and assault, and to come with the same design—­I say, if on firing on those who were guilty, they accidentally killed an innocent person, it was not their fault.  They were obliged to defend themselves against those who were pressing upon them.  They are not answerable for it with their lives; for on supposition it was justifiable or excusable to kill Attucks, or any other person, it will be equally justifiable or excusable if in firing at him they killed another, who was innocent; or if the provocation was such as to mitigate the guilt of manslaughter, it will equally mitigate the guilt, if they killed an innocent man undesignedly, in aiming at him who gave the provocation, according to Judge Foster; and as this point is of such consequence, I must produce some more authorities for it: 

(1 Hawkins. 84):  “Also, if a third person accidentally happen to be killed by one engaged in a combat, upon a sudden quarrel, it seems that he who killed him is guilty of manslaughter only,” etc. (H.  H P. C. 442, to the same point; and 1 H. H. P. C. 484. and 4 Black, 27.)