BAY CITY, Mich. (AP) — A northern Michigan man who said he placed pipe bombs outside phone stores because he was upset with “immoral content” on phones and TV was sentenced Wednesday to more than six years in prison.

John D. Allen’s crimes of “extortion and attempted destruction of cellphone stores were incredibly dangerous,” Assistant U.S. Attorney J. Michael Buckley said in a court filing.

Allen, 76, was accused of placing explosives and threatening notes outside phone stores in Sault Ste. Marie and Cheboygan. “HJ” and “Handcuff Johnny” were written on the boxes, apparently references to Allen. No one was hurt.

Allen, who lives in Whittemore, pleaded guilty to extortion and attempted destruction of a building.

U.S. District Judge Thomas Ludington in Bay City sentenced him to 6 1/4 years in prison.

“He acted alone and does not understand why he made those threats and demands when he knew he couldn’t actually stop pornography,” defense attorney Stevens Jacobs said in a court filing.

Allen will get credit for more than a year already spent in custody.