An explosive device mailed to Maricopa County, Ariz., Sheriff Joe Arapio was discovered by a postal employee Thursday evening.
The package was addressed to Arpaio's Phoenix office, but was intercepted in Flagstaff after a "very astute" postal worker noticed that the package looked odd.
An X-ray scan revealed the explosive device, which was disabled by a bomb squad. Flagstaff is just under 150 miles north of Phoenix.
"The package was neutralized," said Sgt. James Jackson of the Flagstaff Police Department, according to the Arizona Daily Sun. "There was a disruptive device placed on the package and it was disabled."
The Associated Press reports that, according to the Bureau of Alcohol, Tobacco, Firearms and Explosives, the package appeared to contain gun powder. The FBI is investigating the case alongside local police.
"I'm getting many threats," Arpaio told the AP. "This isn't the first time."
The 80-year-old sheriff's hard-charging style has infuriated civil libertarians, supporters of President Barack Obama and advocates for people who reside in the country without legal permission.
Arpaio's office arrested two editors of the Phoenix New Times in 2007 for publishing a subpoena that demanded the IP addresses of readers after the paper published Arpaio's home address. The charges were dropped .
Last year, Arpaio appointed a "cold case posse" to determine whether or not Obama's birth certificate is a forgery. During a March 2012 press conference, Arpaio announced the posse's findings and declared the document a "computer-generated forgery."
Arpaio's disdain for illegal immigration and his unorthodox treatment of prisoners made him a national celebrity. He famously forces inmates to wear pink underwear. A lawsuit filed by the Justice Department's civil rights division in 2012 alleged a "pattern of unconstitutional conduct" against Latinos.