For the window shattering incidents we have considered many possibilities because we have not heard that LE has found any projectile yet in the victims cars/trucks. And some of the windows like the truck window looks like the projectile did not penetrate but just shattered the window and maybe either bounced off or maybe the projectile itself shattered upon impact.
So if we assume for a minute that the perp is using rocks or some other type of ammo like frangibles bullets that break apart, it is possible.
Many years ago I used to hand load my own shotgun shells because I used to have a reloading machine so I learned quite a bit about Primers, powder, cartridges, etc.
My machine was limited to just shotgun shells because you have to purchase specific "dies" for each type of shell. My setup was just for shotgun shells but the procedure is basically the same for any type of shell.
The one thing I found interesting about reloading was that I could put as much or as little gun powder in the shell as I wanted up to a point where it would not be safe to put anymore. I could also reload whatever type of projectile I wanted to in the shell.
So I did some experimenting at the time and I ended up with some unique shells a few of the times. In one case, I reloaded regular BBs and used some extra powder and those shells were powerful. The problem for me with those was the BBs scored the inside of my shotgun barrel so I quit doing that after the first batch.
This is why lead is most commonly used because its soft and doesnt hurt the inside of a gun barrel. As well as lead is heavy and makes a good projecitle.
Back to this case.....It got me to thinking back during those reloading days and I had discussions with friends about how farmers would reload "rock salt" and some of us have likely seen or heard about old movies/stories where we have heard of mean farmers chasing kids off their farms and shooting at them with rock salt.
Rock salt is one of those projectiles that could make glass break and yet the rock salt would explode upon impact and there would be no evidence left.
And I could see where even reloading small round rocks may produce similar results, although rocks would most likely stay in tact. Like if the person was reloading pea gravel into a shell.
Any type of small rock projectile from either gun or slingshot would most likely never be noticed by an investigator if it was laying on the ground outside the vehicle. They would think it was just outside already unless it had something that made it stand out OR if it was found inside the vehicle.
We have discussed so many possibilities and quite a few of them that we have discussed would fit in with LE not being able to find a projectile at the scene for the window shatterings.
I still cant get over seeing the picture of the "Crossbow Slingshot" LOL
That would give the shooter some good accuracy with that thing.