If LE proves a 22 Magnum was used for some of the murders then this actually maybe very important. And here is why. Starting with some background.
I am familiar with most weapons as I have quite a few and even have both a 22 rifle and 22 pistol but this term "22 Magnum" stumped me because I have not heard it used often. The more common "22 Long" is what I thought we were talking about but come to find out there really is a bullet called "22 Magnum" which is actually different than a 22 long and I feel a lot less common than your standard 22.
The link below describes all about it.
When people say a 22 , they are usually meaning a standard .22 caliber round which comes in TWO different forms. Either a .22 Short or a .22 Long. Both have the exact same diameter shell and the difference is in length of shell casing and not diameter. The 22 long round is a little longer and has more gunpowder and has more velocity than a 22 Short round.
There are both pistols and rifles that shoot the standard 22 rounds. A 22 long capable gun can usually shoot a 22 short round but not the other way around. A 22 short capable gun that is made for 22 shorts cannot normally shoot a 22 long round. This is because of the length of the shell.
Now the interesting thing is this 22 Magnum shell which was brought up and which I was not familiar with. So I am assuming it is less common as the normal 22 rounds since I also dont know anybody that has one either. The link describes them and they are more powerful than the 22 Long shell and have an even longer shell than a 22 long. So they have the most gunpowder of all of them.
So the interesting thing about the 22 Magnum is if LE determines that it was used in the shootings then I think this could help LE tremendously since they are not nearly as common as far as people owning them as your standard 22 long or 22 short.
22 Magnum rounds are also referred to as 22 WMR rounds because they were manufactured by Winchester and I think the WMR stands for Winchester Magnum Round.
Hope some of this helps. If not then at least we learned about the 22 magnum round. LOL
https://en.wikipedia.org/wiki/.22_Winchester_Magnum_Rimfire