Silent Joe by T. Jefferson Parker

Scarred for life by a brutal father, Joe Trona found a safe haven and a loving childhood in the home of the couple who adopted him. Now he spends his days as a deputy for the Orange County sheriff's department and his nights as a driver and aide to Will Trona, the influential politician who rescued him from the Hillside Children's Home. An expert in firearms and the martial arts, Joe has been backing Will up for a long time.