March 9, 1878; Agua Negra Canyon, Lincoln County, New Mexico Territory---The Regulators and their two prisoners, Buck Morton and Frank Baker, have spent the previous night at the large South Spring ranchhouse of John Chisum. At some point during the night, the Regulators heard from Chisum or his men that there are rumors going around that the Regulators will be ambushed and Morton and Baker liberated on the road near Lincoln by a large party led by Jimmy Dolan himself and consisting of Morton and Baker's associates. But now it's morning, on the fourth day since Morton and Baker's capture, and the party must resume their trek to Lincoln. They must first stop at the small nearby town of Roswell, though, so that Morton can mail a letter he wrote to a lawyer the night before.
As the party heads towards Roswell, they apparently stop at a small ranch where they encounter a local cowboy named William McCloskey. McCloskey is known by all the Regulators to have occasionally worked for John Tunstall on his ranch, but he's also known to work for Dolan & Co. Stating that he is going to Lincoln too, McCloskey apparently asks if he can accompany the Regulators there. Although none of the Regulators trust McCloskey and aren't sure of his true motives, they reluctantly allow him to ride with them. Morton and Baker, who have both been fearing execution at any moment, are no-doubt relieved to have McCloskey riding with them, since he is a good friend of both of theirs.
The party soon arrives at Roswell, and Morton is allowed to deliver his letter to the local post office. Postmaster Marshall Ashmun "Ash" Upson speaks with Morton and asks him if he feels he'll reach Lincoln alive. Morton replies that he believes he'll live long enough to see Lincoln again, but, he goes on to say, in case he's wrong, he wants his family to be notified of his death. After saying this, McCloskey steps forward and tells Morton, "Billy, if harm comes to you two, they'll have to kill me first." McCloskey apparently doesn't notice the ever-vigilant Regulators standing close enough to him to hear his words. After this, the Regulators, their prisoners, and McCloskey head out, once again heading towards Lincoln.
Near the small village of Picacho, the Regulators turn off the main road and head down through Agua Negra Canyon, in order to avoid the Dolan party that is allegedly waiting to ambush them on their way to Lincoln. Morton and Baker, given no explanation for this unexpected course of action, grow nervous once again. A short time later, the Regulators emerge from the canyon; Morton, Baker, and McCloskey, however, remain on the canyon floor, their bodies riddled with bullets.
What exactly happened in the canyon that ended with the deaths of Morton, Baker, and McCloskey will never be known. There are several versions of what transpired, though. The most popular version, as told by Ash Upson, is that Regulator Frank MacNab rode up beside McCloskey's horse, pulled out his pistol, put it to McCloskey's head, said "So you're the sonofabitch that's got to die before harm can come to these men, huh?" and pulled the trigger. McCloskey's body fell to the ground, and Morton and Baker, panicking, took off, only to be gunned down by the rest of the Regulators. Another version, told by most of the Regulators, is that Morton, fearing execution, rode up beside McCloskey, grabbed McCloskey's gun, shot him, and tried to run, only to be gunned down, along with Baker, who also was fleeing. This seems highly unlikely. Why would Morton kill the only friend he had in the bunch, one who pledged that he would have to die before Morton himself could? Furthermore, how could Morton and Baker honestly expect to escape from thirteen well-armed and alert men with two pistols (the Regulator also later claimed that Baker had a small pistol hidden on his body as well) and two very tired horses? A third version is that Billy Bonney again suggested that they just kill Morton and Baker, whereas McCloskey protested, only to be shot by Billy himself. Morton and Baker panicked, took off, and were gunned down by all the Regulators. A fourth version is that the Regulators deliberatly took the Agua Negra Canyon trail in order to execute Morton and Baker without witnesses. When McCloskey voiced an objection, he was also gunned down. This also seems highly unlikely, since if they wanted to kill Morton and Baker, they would have just done it when they first captured them, and not go through the hassle of having to make them ride with them for four days. In my personal opinion, I think what may have happened is that McCloskey thought they were taking the Agua Negra Canyon so the Regulators could kill Morton and Baker. McCloskey then tried to secretly slip Morton or Baker a pistol. One of the Regulators saw this, shot down McCloskey, and then the rest of the Regulators gunned down Morton and Baker as they ran in a panick.
Whichever version, if any, is true, after the killings most of the Regulators head to the small Hispanic village of San Patricio, where they begin to make their headquarters and haven. Frank MacNab rides back to the Chisum South Spring ranch alone, presumably to inform Old John about what had just happened. Dick Brewer, however, rides into Lincoln himself, where he is informed that, earlier in the day, Gov. Samuel Axtell had revoked Justice of the Peace John Wilson's status and rendered all of his acts in that capacity void. This act meant Dick was never a constable to begin with now, and the Regulators were not an official posse either. It also meant that the killings of Morton, Baker, and McCloskey were not in anyway official. To sum it all up, the Regulators are now full-fledged outlaws. After getting the news, Dick leaves Lincoln and heads back to San Patricio, to deliver the bad news to his compadres.
Regulators involved
Murphy-Dolan-Riley men involved
