Local Phoenix affiliate Fox10 reports that Arpaio said the new rifles are essential to help local police combat criminals who are using increasingly powerful weaponry.
"We live in a violent society, even here in Maricopa County, and across our nation, and the least we can do is to arm our deputies, let's say with enough firepower to fight back."
But the news that he is requiring the deputies to be armed and essentially on duty at all times is noteworthy.
"My deputies will carry guns 24 hours a day, even off duty. If they see any incident occurring, they will take action anywhere in this valley," he said.
Arpaio says the 400 new Smith & Wesson rifles were purchased using money obtained from arrests. The 81-year-old self-described "America's toughest sheriff" is no stranger to controversy, stemming primarily from his strict enforcement of the state's immigration laws.
Local affiliate ABC15 reports that the deputies will be required to carry only a handgun at all times, meaning they will have to employ the AR-15 style rifles only while on duty.
“While this decision may seem controversial to some in the public and among other law enforcement agencies, I have extreme confidence in the training and professionalism of the men and women deputies in the Maricopa County Sheriff’s Office,” Arpaio said at a news conference on Thursday.
Fox10 notes that the announcement came on the same day that a Sheriff’s Office employee, Jorge Vargas, was shot and killed outside his home while off duty.
The Sheriff’s Office says that three deputies have been shot and killed in the line of duty over the past two years.