The Moscow concert hall attack

 https://www.bbc.com/news/world-europe-68650914

Unfortunately, the+Moscow+concert+hall+attack is one of various locations where such horrible things can happen.

https://www.theguardian.com/world/live/2024/mar/25/russia-ukraine-us-islamic-state-concert-hall-attack-live-latest-news

https://www.themoscowtimes.com/2024/03/24/terrorists-have-no-nationality-tajik-president-tells-putin-a84602

https://www.theguardian.com/world/2024/mar/25/moscow-crocus-city-concert-hall-shooting-details-is-islamic-state-vladimir-putin

https://www.telegraph.co.uk/world-news/2024/03/23/moscow-crocus-concert-hall-islamic-state-attack-many-killed

https://thedigitallabyrinth.blogspot.com/search?q=Vladimir+Putin

A concert hall in Moscow and in the movie, TENET

 https://www.aljazeera.com/news/2024/3/22/gunfire-and-explosion-reported-at-concert-hall-in-russias-moscow

Given as to how many books, movies & TV productions there are, its likely that there will be an occasional intersection of similar events. 

https://www.denofgeek.com/movies/tenet-opening-scene-opera-explained

Of course such similarities might not always occur in the same location, year, decade or era. 

https://apnews.com/article/russia-moscow-gunmen-concert-hall-injuries-fe7db5bb4ad4df17b6cbd04a3250faa1

https://www.vulture.com/article/tenet-is-a-backward-movie-for-an-upside-down-world.html

https://www.rogerebert.com/features/tenet-rerelease

https://thedigitallabyrinth.blogspot.com/search?q=the+Moscow+concert+hall+attack

https://thedigitallabyrinth.blogspot.com/search?q=TENET

Did Russia ignore US 'extremist' attacks warning?

 https://www.bbc.com/news/world-europe-68646375

Given the place and time, the+Moscow+concert+hall+attack should have had a perimeter of armed security. A Concert-hall, especially in a big city, should have a higher level of security like arenas and stadiums...

A Russian security failure?

 https://www.reuters.com/world/europe/russian-security-failure-kremlin-says-no-country-is-immune-terrorism-2024-03-25/

Since Russia is in a state of war, one would think that they would be better prepared to handle internal violent situations.

https://en.wikipedia.org/wiki/Federal_Security_Service#Counterterrorist_operations

https://www.theguardian.com/world/2024/mar/24/did-ukraine-war-russian-security-services-neglect-islamist-threat-moscow

Of course if some group is very determined, they will keep looking for an advantage.

https://www.themoscowtimes.com/2024/03/24/russian-opposition-blasts-putins-broken-security-promises-after-moscow-attack-a84605

https://www.aljazeera.com/news/2024/3/25/fear-stalks-russia-after-moscow-massacre-as-putins-allies-play-blame-game

https://en.wikipedia.org/wiki/Federal_Security_Service#Creation_of_the_FSB

https://en.wikipedia.org/wiki/Federal_Security_Service#Role_in_Ukraine

https://thedigitallabyrinth.blogspot.com/search?q=the+Moscow+concert+hall+attack