A man who killed at least 5 people was put to death...

A man who killed at least 5 people was put to death in McAlester for murdering a Noble County couple in 1990. Robert Knighton, 62, was pronounced dead at 6:32 p.m. Knighton shot and killed Richard and Virginia Denney, 64, on Jan. 8, 1990, during a 3-day crime spree that began with the murders and robbery of Frankie T. Merrifield and his stepson, Roy E. Donahue, in Clinton, Mo. Knighton becomes the 8th condemned inmate to be put to death this year in Oklahoma and the 35th in the USA.