Fr. Adrian Fortescue (of liturgical fame) shot and killed a man in self-defense.

http://unavoce.org/uva-archive/adrian-fortescue-priest-and-scholar/

“Adrian Fortescue was a stouty built, full-blooded man, of great physical strength and
of true manly virtue in the classical sense. This stood him in good stead during his
journeys to the wild and remote places that he loved so much. Once at least he fought for
his life. On one occasion he was engaged in a hand-to-hand struggle with some fanatical
Albanian soldiers at Hebron, and he and his companions had to fight their way with
bludgeons to their horses and gallop away, in Adrian’s case with a broken collarbone. On a
second occasion the caravan with which he was travelling in Asia Minor, disguised as an
Arab, was attacked by brigands, and in self-defense he killed an assailant with a pistol
shot. He mentioned this incident in a letter to his close friend Father Harold Burton in
1907:

Quote

I have just come back from a year spent in Syria, Mesopotamia. Asia Minor & Greece.
I saw many and wonderful things. I rode long days across the great Syrian desert, alone
among Arabs. I stood anong the ruins of strange dead Greek cities in Asia Minor &
slept on the bare earth under broken white columns where Diana of the Ephesians had once
reigned as a mighty god. And I saw forests & climbed mountains and crept through deep
passes in the heart of Asia Minor. I went a pilgriming to the holy places too, said Mass
at the holy sepulchre, spent the night of Maundy Thursday on the Mount of Olives & saw
the Easter sun rise above the golden walls of Herod’s temple. Then there were Damascus,
the slow brown waters of the Euphrates, the orchards of Galilee, Cyprus (a heavenly
island), the tawny pillars of the Athenian Acropolis, the fat plains & strange
Byzantine monasteries of Thessaly; and- far most glorious of all – the line of domes and
minarets, radiant, white & fretted like carved ivory against a hot grey-blue sky, that
crown imperially Constantine’s New Rome by the Bosphorus. So you see I have had a purple
time. I have learned to talk Syrian Arabic quite well & some Turkish. Greek I could
talk already; & now I work at Persian like a horse, greatly hoping to go out again in
a year or two & next time to reach Teheran & Shiraz. Also I made a heap of
drawings and learned much about Mohammedan ideas. But I suffered a great hunger &
thirst & heat, was under fire from robbers & Bedawin several times; once I saved
my life by flight leaving all my baggage to the spoiler, once I shot a man dead (a horrid
memory): I had my shoulder smashed to bits in a fight at Hebron & lay six weeks sorely
sick in the French hospital at Jerusalem, & I nearly died of malarial fever at Aleppo.
Such is the outline. To hear more you must come to see me, as I very much hope you will.
Now I shall not go back to Maldon, but I am to start a new mission at Letchworth in
Hertfordshire – where this new Garden City place is. I an very pleased with the idea
indeed.“

Interesting! Now if he just had some Hydroxycholoroquine? He would have had a better time with his malarial fever, AND be covered to help prevent Covid-19, LOL.

The section below is from Prummer's Handbook of Moral Theology. Note the propositions limiting the principle by two Popes after St. Thomas Aquinas's time.

Even the secular self-defense luminaries teach "Stop the attack." It can never be "Kill the attacker."

If the defense kills the attacker, it must be because it was necessary to stop the attack.

Anything else will get you in trouble both in Heaven and on this Earth.