A note from Pope John Paul II:
"......Certainly, the intrinsic value of life and the duty to love oneself no less than others are the basis of a true right to self-defense ... legitimate defense can be not only a right but a grave duty for someone responsible for another's life, the common good of the family or of the State. Unfortunately, it happens that the need to render the aggressor incapable of causing harm sometimes involves taking his life. In this case, the fatal outcome is attributable to the aggressor whose actions brought it about, even though he may not be morally responsible because of a lack of the use of reason." - Pope John Paul II, Encyclical Letter from 1995, EVANGELIUM VITAE
St. Gabriel Possenti...The Patron Saint of Handgunners
One a summer day a little over a hundred years ago, a slim figure in a black cassock [Possenti] stood facing a gang of mercenaries in a small town in Piedmont, Italy. He had just disarmed one of the soldiers who was attacking a young girl, had faced the rest of the band fearlessly, then drove them all out of the village at the point of a gun....[W]hen Garibaldi's mercenaries swept down through Italy ravaging villages, Brother Gabriel showed the kind of man he was by confronting them, astonishing them with his marksmanship, and saving the small village where his monastery was located."
Saint Gabriel Possenti's "astonishing marksmanship" was displayed after he had just disarmed the soldier. The mercenaries' leader told Possenti that it would take more than just one monk with a handgun to make the mercenaries leave town. The saint pointed out to the mercenaries a lizard which was running across the road. Possenti shot the lizard right through the head, at which point the mercenaries decided that discretion was the better part of valor; they obeyed Possenti's orders to extinguish the fires they had started and to return the property they had stolen. They then fled the village, never to be heard from again.
Possenti was canonized by Pope Benedict XV in 1920. He died in 1862 and his feast occurs on February 27th.