U.S. prosecutors said Wednesday they will not seek the death penalty as part of a plea agreement with the man charged in the political assassinations of the top Democrat in the Minnesota House along with her husband, as well as the attempted murders of a state senator and his wife.

A Minnesota man who posed as a police officer and knocked on lawmakers' doors in the middle of the night, killing the top Democrat in the state House and her husband and wounding a state senator and his wife, pleaded guilty to murder on Thursday so that federal prosecutors would not seek the death penalty.