Legitimate defense can not only be 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 action brought it about.

– Evangelium Vitae, section 55

A fuller examination from Mr. Michael T. Barry. (h/t Wife) Please click through and read.

So despite what some “Catholics” might feel and say about gun control, they do not speak for The Church and one should not mistake their opinion for dogma.