The following is part of what appeared in this week's bulletin by a traditional priest last Sunday.  It's in anonymous for obvious reasons.

"What is a real man?  At Holy Mass, for instance, if you are a man, you are ON DUTY.  Security is one of the things you provide as a provider.  In addition, you are to initiate.  Initiate relationships, solve problems, engage the enemy.  Men don't wait to be asked.
 
The parish church is for worship.  Anyone here for another purpose is trespassing.  All trespassers whould be encouraged to leae, including pan handlers, protesters, or criminals.
Men, be prepared to act alone, but never let another act alone.  If an incident is developing, one man can marshal support by saying the word, "security".  At the sound of this, ALL men will respond by going to the call, not wasting time looking and wondering.  Go to the danger, put yourself in harm's way.  The choices are not between life and death, but these:  die as a hero, or die as a coward.  "Greater love hath no man, than to lay down his life for his friends."
 
Meet the difficulty appropriately.  Protesters, for instance, should be politely, but firmly addressed with an "I" statement:  "I need to see you outside pleasel"  Avoid "you" statements, as these lead nowhere.
 
Engage en masse.  If one protester is engaged by one security officer (you), or engaged by ten standing united, which situation will resolve more quickly, peaceably and easily?  Never use physical force unless defensive.  That said, use your physicality to control, for instance standing between the protester and the congregants.
 
Are you allowed in the sanctuary?  Yes, jump the rail if you have to, there'll be time enough for kneeling, when the dealing's done.
 
What if an active shooter appears?  Meet violence with violence.  Engage the enemy quickly en masse and in force.  How many "Campian Hymnals" could someone take to the head before being overwhelmed?  Woman, what should you do?  After getting your husband's attention, hand him a hymnal, take the children and head for safety, one call the police while the rest pray.
 
Can we train to be a hero?  Yes!  Don't hit the "snooze" button on your alarm.  This is heroic training of your will:  say no to a lower, present good for the sake of the higher, future good.  Come to morning Mass."

Bravo!

Some more practical advice in the case of a shooter:

Armed men should take positions near the center aisle in the first and last rows (this will be the shooter’s entrance and/or destination point, and you’ll be better positioned to take a clean shot and avoid hopping over people to get one off).

Take a knee and aim for a head shot or upper torso: This trajectory makes it less likely you will hit the innocent if you miss or overpenetrate.  Be prepared for panicked faithful to obstruct your line of fire, and be disciplined and deliberate with your shot selection.

Italian-American response to "guests" who misbehave

https://youtu.be/akY0mf1G-Cs?t=100

https://www.knightsrepublic.com/church-defense

Not sure, but he would be Novus Ordo (i.e., they are a conservative NOM group).  I post it for their tactics.

If it was written by the Neo-SSPX, it's oblivious and tone deaf.  Hey Trad men, be cannon fodder for the same people & priests who are in part responsible for the way things are now. "I mean we compromised the Faith, capitulated to the "elder brothers", pushed Tradfeminism, open borders, political correctness, anti-racism, gαy-straight alliances, the covid hoax, but would you men take a bullet for us?" 

It boggles my mind that many of you here can't see that. Then again after much of the discourse on this site over the past two years, I'm afraid even the SSPX Resistance here in the States is on thinner ice with many of us.