Here's an account of the event from Bill O'Neal's Encyclopedia of Western Gunfighters.
"September 4, 1887, Holbrook, Arizona.
On a Sunday afternoon Owens rode up to the Holbrook house of widowed Eva Blevins, who recently had lost her husband and one of her four sons in the Pleasant Valley War. Owens was looking for her boy Andy "Cooper," who had adopted an alias because he had killed two sheepmen in the Pleasant Valley feud and because he was sought by Texas authorities for past misdeeds. Owens approached the house with his Winchester cradled in his arms, and he spotted Andy, armed with a six-gun, peering through one of the two front doors. Owens and Andy fired simultaneously, and the lawman's bullet plowed through the door and sent Andy staggering back into the arms of his mother. Then John Blevins squeezed off a shot from the other front door, and Owens, still firing from the hip, shot him in the right shoulder. Owens ran to the side of the house just as Mose Roberts, a Blevins brother-in-law from Texas, hopped out a rear window brandishing a revolver. Owens dropped Roberts with one shot, then wheeled to meet another threat. The youngest Blevins boy, sixteen-year-old Sam Houston, ran onto the front porch with a six-gun, but Owens drilled him in the heart. Owens fired a few more shots through the thin walls of the house, but there was no one besides Eva Blevins and two other women left standing. Owens rode off, leaving only John Blevins to survive the shootout."