Arizona authorities say a package addressed to Sheriff Joe Arpaio discovered in a northern Arizona mailbox would have exploded if opened, leading to serious injuries or death.

Maricopa County Chief Deputy Jerry Sheridan made the comment Friday at a news conference in Phoenix. He said investigators are trying to locate one person who may have been involved in mailing the package addressed to his boss.

The package intercepted late Thursday was addressed to Arpaio at his downtown Phoenix office. It had been left in a parcel locker that was part of a multiple address mailbox in a rural part of Coconino County, outside Flagstaff city limits.

U.S. Postal Inspection Service spokesman Keith Moore said a courier called his supervisor after noting it was suspicious, and the package was eventually brought into the main Post Office in Flagstaff. An X-Ray showed what appeared to be bomb-like components, including wires and a container, and authorities used a water cannon to neutralize the package, Sheridan said.

Arpaio, the self-proclaimed “toughest sheriff in America,” said this isn’t the first time he’s been threatened. Arpaio is known nationally for his strict treatment of jail inmates and cracking down on illegal immigration.

“Of course you worry. I’m a victim, I’m a witness. When you convict people, the victim has to be somewhat concerned. I’m a little concerned about my family,” Arpaio said at the news conference. “I didn’t ask for all these threats.”

Postal Inspector Patricia Armstrong said authorities were alerted by a “very astute” carrier who observed “something suspicious” about the package.

Armstrong didn’t elaborate on what raised suspicion, but Tom Mangan, a spokesman in Phoenix for the federal Bureau of Alcohol, Tobacco, Firearms and Explosives, said initial reports indicated that the package was a box that might have been damaged in transit and leaked gunpowder.

Sheridan said the package contained black powder and an ignition device, although he wasn’t sure if it was packed into a container and would have exploded or simply ignited in a flash fire. Either way, he said, it was very dangerous.

“Had someone opened that package, it would have caused a major explosion and caused serious physical injury, burns and maybe death,” Sheridan said. “That is a very, very serious threat.”

Authorities in Flagstaff, which is about 140 miles north of Phoenix, said they are pursuing leads in the case.

Arpaio said he receives lots of packages, including ones with cookies recently as he recuperated from a broken shoulder suffered when he fell crossing a street on his way to lunch. He said he opens some of the packages personally.

“Hey, they send me cookies, now they send me bombs,” he said Friday. “It’s a little different.”

Arpaio said the mailing of an explosive device addressed to him comes with his line of work. He cited the recent killings of a West Virginia sheriff, Colorado’s corrections director and two prosecutors in Texas.

“That’s the nature of the business,” he said.

Arpaio said whoever is responsible for mailing the package, if found, would be brought to justice.

“I’m not going to be intimidated by anyone, that’s a promise,” he said.

Following the killing of a West Virginia sheriff last week, Arpaio said elected law enforcement officials across the nation seem to be targeted.

Arpaio has had a security detail for years, and regularly receives threats. This week, the sheriff’s office said he had received threats from Mexican drug cartels which put a $4 million bounty on him and possibly dispatched a hit man to attack him.