[Nervous Tick]

>> subsonic ammo that did not have enough power to work the semiautomatic action and he had to manually recycle the bolt between shots

good point

If so there should be at least two casings in addition to three cartridges on the ground. Wonder what the other two had written on them, if anything?

[E. Pluribus Unum]

...there should be at least two casings in addition to three cartridges on the ground. Wonder what the other two had written on them, if anything?

.22 LR casings are pretty small. I can see them not being able to find them all on a city sidewalk/street.

[DesertRhino]

No, it was a silencer equipped large pistol, and had a slide lock device on it. Made it much more quiet by keeping gasses from escaping the ejection port. It’s the ultimate in quiet. But it requires you to run the action manually after each shot.
Most people running silencers don’t need or use them.

[Blue Highway]

Drink . More . Ovaltine.

[DCBryan1]

Either that or no Neilson device on it (or a very dirty one).It is also known as muzzle boosters and exist to help short recoil guns cycle properly and overcome the excessive weight at the end of the barrel.

It would be VERY quiet, however, failure to cycle is a byproduct.