An email from the sheriff's office said the decision was due, in part, to the fact that "Sheriff Arpaio is a recently targeted recipient of an explosive device."
A package containing an explosive device and addressed to Arpaio was intercepted April 11 near Flagstaff.
Officials said the package would have exploded if opened, leading to serious injuries or death.
It had been left in a parcel locker in a rural part of Coconino County, outside the Flagstaff city limits. U.S. Postal Inspection Service spokesman Keith Moore said a courier brought it into the main Post Office in Flagstaff. It was X-rayed and the device was detected. A bomb squad used a water cannon to neutralize the package.
It's been that kind of a week -- "interesting times" as the apocryphal 'old Chinese curse' (actually a more modern western invention) condemns us to live in.
Add the mail bomb threat against Sheriff Arpaio to this week's disturbing, unsettling and tragic list of events in the life of the Republic:
The Boston Marathon bombing on Patriot's Day (Monday)
The "ricin letters" delivered to lawmakers on Capitol Hill (Tuesday)
The fertilizer plant explosion in West, Texas, north of Waco.(Wednesday)
Still awaiting word from Salon.com contributor David Sirota on his hopes for the race and sex of the Arizona mail bomb perpetrator.