Pat was eight or ten years older than Billy the Kid. This made no difference, however, as they became good friends, playing cards together, riding out into the country together, drinking, and attending the fan dangos together, and were known as "Little Casino" and " Juan Largo" or Long John. Garrett finally got married, his Polinaria Guiterrez bearing him seven children. 

Garrett was elected sheriff of Lincoln County in 1,880 at an opportune time, for certain officials who had an eye on the Kid who had gone bad in the Lincoln County Cattle War, had put a price on his head. Gover nor Wallace decided to turn Pat on the trail of his old playmate and comrade, the Kid, feeling that Garrett would know all his habits and hideouts. 

Garrett's first try at tripping up the Kid failed. At Fort Sumner he shot and killed the Kid's lieutenant, Tom O'Folliard. Billy skipped out. Pat kept on his trail, however, and at Stinking Spring, in September of 1880, a shoot-out resulted, Charlie Bowdre being killed. The Kid finally walked out of the shack, Pat luring him with the smell of food over the fire and many promises. Along with 'the Kid were the notorious Dave Ruda baugh, Tom Pickett and Billy Wilson. Pat fed them well and then took them on into the Santa Fe lockup. After one or two more escapes, Pat again captured the Kid and took him on to Lincoln, where he had been sentenced to hang. During Pat's absence, the Kid killed both of his  guards and escaped to Fort Sumner, where he hid out at Pete Maxwell's place. Pat rode out after him, and hiding in Pete's bedroom one night, shot the Kid when, he walked into the dark bedroom, not sus pecting that the sheriff sat there with a gun pointed at him. 

Pat was severely criticized for what he had done. Many thought one of the Mexicans or friends of Billy would cut him down. They said that Billy had been unarmed with only a butcher knife in hand as he had returned from the smokehouse where he had cut some beef. 

But there was glory in it for Pat. Every newspaper in the land shouted the great news of what the New Mexico sheriff had done. There was the business of a $500 reward, too, and Garrett had to hire a lawyer and go into Santa Fe to persuade the State Legislature to pass a special act so he could collect. 

There were no more praises now, as things settled down in New Mexico. Pat went into the cattle business in Fort Stanton, sold out and joined the Home Rangers, who hunted down rustlers in the Canadian River country. He soon tired of this, too. Restless and ill-at ease, he became cattle boss for Captain Brandon Kirby, a large British outfit operating in Lincoln County. Many hard looks met Pat at every turn from ranchers and townsmen; he felt their disapproval at what he had done to the Kid. He had written- a book by this time and its publicity was well received outside of New Mexico. But hometown acclaim was nil. His heroism boomeranged, despite Teddy Roosevelt's praise, and Pat grew sour and crabbed, men shunned him in many places. 

He quit Kirby in 1886 and went to ranching in Ros well, New Mexico. He failed. He ran for sheriff of Chaves County. He failed again. He went on to Uvalde, Texas, where he took up breeding horses. Here he did make a friend of "Cactus" John N. Garner who got Pat elected as the County Commissioner. A few true friends in New Mexico prevailed upon Pat to return and run for sheriff again. This was done and he served a single term and then resigned. He purchased a ranch in Las Cruces in the Organ Mountains. 

Pat leased out this property to a young rancher by name of Wayne Brazil, then tried to force him off the property over an argument on the running of sheep. Brazil, a hotheaded man, shot and killed Pat as he went for a shotgun in the back of a buckboard.

Garrett was buried in Las Cruces. There is no marker on the grave and today few people know where it is. They say it is a bleak and haunted place where only the weeds grow and an occasional coyote can be heard as it howls a thin, wavering note into the night.