Original sentence: Eric David Harris (April 9, 1981 – April 20, 1999) and Dylan Bennet Klebold (September 11, 1981 – April 20, 1999), both high school seniors, were the mass murderers of the Columbine High School massacre
Edited sentence: Eric David Harris (April 9, 1981 – April 20, 1999) and Dylan Bennet Klebold (September 11, 1981 – April 20, 1999), both high school seniors, were the mass murderers and cold blooded killers of the Columbine High School massacre