>"I am not a gun guy, so I don't even know the diff between semi/fully."
It is fairly simple. A semi-automatic will fire a round each time the trigger is pulled. A full-automatic (or just "automatic") will continuously fire rounds, as fast as possible, as long as the trigger is held in. A "select fire" is [almost always] a rifle, and can be changed between semi-automatic and automatic (and sometimes "burst") modes with a selector on the weapon.
>"What I do know is rifles semi/full are the ones responsible for the really deadly ones."
Only semi-automatics, when it comes to mass shootings. Full automatic rifles have not been documented in any mass shooting. Yes, semi-automatic rifles are, generally, far more potentially deadly than handguns because they are much easier to control, are more accurate, have larger ammunition options, and higher velocities. Their main drawbacks are large size and weight, and lack of concealability.
>"Semi-automatic assault weapons have been used [...]"
There is nothing special about the nebulously so-called "assault weapons". For all intents and purposes, they are just modern, semi-automatic rifles. It is just the appearance and a few accessory features that end up having a scary label placed on them. A modern, semi-automatic hunting rifle is just as deadly, shoots and loads at the same speed, but it is less "scary" looking.
>"he chose a semiautomatic rifle because itâ(TM)s âoevery deadly.â"
As opposed to a manual rifle? Those are pretty rare.
>"Growing up in the 60's were even semi auto's available?"
Yes. Since 1885. But it took several more decades to become more available and standard.
>"As a kid, a rifle meant a 22, which I think I fired once in my life at a camp, and it seemed like a pretty slow fire rate, but that was a very long time ago and I was a kid."
A ".22" is just the caliber. That doesn't denote if it is semi-automatic or not. Nor if it is a rifle or pistol.
A non-semi-automatic (manual/single shot) weapon requires the user to cycle the mechanism (to eject the spent cartridge and load the next one) by hand, before the trigger can be pulled again. There are lots of semi-automatic 22 pistols and rifles, as well as many other calibers, and also shotguns.
>"Just looked there is a report https://abcnews.go.com/US/memo... [go.com] that the pistol was fully automatic [...]
Apparently the "Glock switch" is easy to add afterwards.
That is not a true automatic weapon. The so-called "Glock Switch" is for handguns (pistols) only, and it is an illegal modification. The resulting weapon is usually much WORSE for defense (and effective offense) because it is inaccurate and difficult to control.