NOGALES, Ariz. - Teams of border officers combed through the Arizona desert about 10 miles north of Mexico on Thursday in search of the lone outstanding suspect in the fatal shooting of a Border Patrol agent. They were on horseback and all-terrain vehicles searching rugged, hard-to-reach spots in a mountainous area just north of Nogales in southeastern Arizona. Officers in patrol cars were searching the perimeter. The suspect could be in Mexico, or could have tried his luck in Nogales or a nearby town, but he also could be hiding behind the next bush. ...authorities have four suspects in custody...