One of the guards at Silo 16 asked the Tenth Doctor, Martha Jones, Jack Harkness and Padra Toc Shafe Cane to show him their teeth when they approached the gates. He later killed a Futurekind for sabotaging the rocket's equipment.
Jack sarcastically told the Doctor to put his gun down which the Doctor replied that he "[wasn't] my responsibility". (TV: Utopia)