BISMARCK, N.D. (AP) — A convicted ax murderer serving a life prison sentence in North Dakota has been given an additional 40 years for attacking a prison guard.

John Bridges pleaded guilty on Tuesday to felony charges of attempted murder and possession of contraband and was given the maximum 20-year sentence on each count. Judge Bruce Romanick called Bridges "a dangerous person."

Authorities said that Bridges stabbed officer Daryl Lawson on Aug. 25 with a homemade knife at the North Dakota State Penitentiary. Lawson's wounds were considered minor.

Bridges is serving a sentence of life in prison plus 20 years for the July 2012 kidnapping and ax murder of Lee Clay. Bridges acknowledged that he forced Clay into his van and killed him during a struggle on Interstate 94 in Burleigh County.

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