After pledging allegiance to to Tunstall, the Kid plodded along for some months in the monotonous groove fashioned for the "cow boy." In his bearing one would never detect the dare-devilism which had heretofore characterized him. He frequently came in contact with his employer and entertained for him strong friendship and deep respect, which was fully reciprocated by Tunstall. He was also ever a welcome guest at the residence of McSween. Both Tunstall and McSween were staunch friends to the Kid, and he was faithful to them to the last. His life passed on uneventfully. Deeds of violence and bloodshed were of frequent occurrence on the Pecos and in other portions of the country, but all was quiet on the Rio Feliz. The Kid had seemed to lose his taste for blood. He was passive, industrious, and, seemingly, content. It was the lull before the storm.

In the month of February, 1878, William S. Morton (said to have had authority as deputy sheriff), with a posse of men composed of cow boys from the Rio Pecos, started out to attach some horses which Tunstall and McSween claimed. Tunstall was on the ground with some of his employees. On the approach of Morton and his party, Tunstall's men all deserted him - ran away. Morton afterwards claimed that Tunstall fired on him and his posse; at all events, Morton and party fired on Tunstall, killing both him and his horse. One Tom Hill, who was afterwards killed whilst robbing a sheep outfit, rode up as Tunstall was lying on his face, gasping, placed his rifle to the back of his head, fired, and scattered his brains over the ground.

This murder occurred on the 18th day of February, 1878. Before night the Kid was apprised of his friend's death. His rage was fearful. Breathing vengeance, he quitted his herd, mounted his horse, and from that day to the hour of his death his track was blazed with rapine and blood.