A common statement, attributed to one mass murderer of unarmed victims was that after the first one, all the rest were free.
Back in 2007 after the Christmastime Colorado Springs church shootings halted by an armed parishioner one of our local ministers asked those in his flock who were armed to stand so that their fellow churchgoers could see who of us would be putting their lives on the line should such a thing come to our area. About a dozen of us did so, following which the pastor then pulled back his coat jacket to let it be seen that he too was stnding with us.
He then read to us the lesson for the day, from the Book of Luke, 22, verses 35-39
And he said unto them, When I sent you without purse, and scrip, and shoes, lacked ye any thing? And they said, Nothing.
Then said he unto them, But now, he that hath a purse, let him take it, and likewise his scrip: and he that hath no sword, let him sell his garment, and buy one.
For I say unto you, that this that is written must yet be accomplished in me, And he was reckoned among the transgressors: for the things concerning me have an end.
And they said, Lord, behold, here are two swords. And he said unto them, It is enough.
And he came out, and went, as he was wont, to the mount of Olives; and his disciples also followed him. 
Personally, I kind of prefer Deuteronomy, 41/42.