A Portland man who contends the government killed his brother pleaded guilty to one count of threatening to destroy a building with explosives and will be sentenced next month.

Forty-five-year-old David Nelson was arrested in November after members of Portland's Joint Terrorism Task Force connected him with bomb threats. In a plea deal filed in federal court prosecutors will drop additional charges and recommend Nelson face five years of probation, with the conditions that he submit to mental health treatment.

In court papers, Nelson wrote that he suffers from paranoid schizophrenia and post-traumatic stress disorder. His criminal history includes a 2006 criminal mischief conviction for breaking a window at a building that housed US Senator Gordon Smith's Portland offices.

Nelson is also accused of leaving threatening messages at the offices of federal lawmakers. The caller to those offices frequently said the government was responsible for using radio frequencies that killed his brother.

Nelson regularly called The Associated Press bureau in Portland in 2006 and 2007, pressing for an investigation into the 2005 death of his 44-year-old brother.