"To ignore the problem of gun violence where two of the worst shootings in US history took place - Aurora and Columbine - would not only be noticeable by its absence but would slight the memories of our loved ones killed," the letter said.
James Holmes, a former neuroscience graduate student, has been charged with murder and attempted murder in the July 20 rampage, one of the worst USoutbursts of gun violence in recent years. In addition to those killed, 58 people were wounded.