WHITTEMORE, Mich. — A northern Michigan man said he placed pipe bombs outside two phone stores because he was upset with “immoral content” on phones and cable TV, according to the FBI.

Authorities filed charges Tuesday against John D. Allen of Whittemore, less than a week after explosives and notes threatening Verizon and AT&T were found at phone stores in Sault Ste. Marie and Cheboygan.

The boxes also contained handcuffs. “HJ” and “Handcuff Johnny” were written on the boxes, apparently references to Allen, the FBI said. No one was hurt.

Allen, 75, was confronted by agents Monday and said he acted alone.

“Allen stated that he created and placed the letters and bombs because he became dissatisfied with all of the immoral content, including pornography, on phones and cable television,” the FBI said in a court filing.

Allen also is accused of writing letters found last month at communication towers across Michigan’s Upper Peninsula. The letters made threats and claimed to be from the “Coalition for Moral Telecommunications.”

Allen appeared in court on charges of extortion and attempted destruction of buildings. A message seeking comment was left for his attorney.

Photos from the Mackinac Bridge and video from the phone stores greatly helped agents.

Allen used a California license plate at one point but said “he realized that he had made a mistake when he noticed the emblem for the auto dealership on the rear of the vehicle could not be removed,” according to the FBI.

Indeed, agents got information about Allen, the owner of the 2006 Chevrolet Uplander, after visiting a dealer in Standish.

Since the explosive devices were discovered Thursday afternoon, special agents, intelligence analysts, troopers, deputies, and officers from the FBI, Michigan State Police, Cheboygan County Sheriff’s Office, Cheboygan Police Department, Sault Ste. Marie Police Department, and Sault Ste. Marie Tribal Police, the US Coast Guard, US Border Patrol and ATF have been working around the clock to identify and apprehend this subject.

“I am so proud of the patrol officers, detectives, and agents that were and are involved in this investigation. Their dedication, determination, and team work is very impressive,” said Sault Ste. Marie Police Chief Wesley Bierling in a statement posted on the department’s Facebook page.