Battle of Los Angeles

As mentioned close to the bottom of that article, another take on it was that it involved UFOs:

https://losangeleno.com/strange-days/battle-of-los-angeles/

As mentioned in the See Also, Spielberg’s movie 1941 idea was based on this.

https://youtu.be/6_KOLqpo7z8

If you read a decent bit of WW2 history, incidents like this are fairly common. A bunch of young men in a high-stress situation open fire on phantom targets. Once one person / group starts shooting everyone else tends to join in unless command prevents it.

Reminds me of https://en.m.wikipedia.org/wiki/Operation_Cottage