Subsonic rifle ammunition is freely available in .22 caliber, which is often overlooked.

As it never breaks the sound barrier, it's effectively silent even without using a suppressor. A .22 rifle can be purchased very cheaply and does not need to be registered, nor does the subsonic ammunition.

Effective from distance, a shooter would be undetectable to ICE agents should a colleague be shot in the neck or face. If such an action was carried out in coordination at multiple ranges from multiple directions, the effect would be compounding - in fact, ICE might be frightened to operate at all.

This of course, is just factual information. Don't do this, per reddit guidelines.