One would have to walk about the crash site with a weapon that is comparable to a overly pregnant 50 cal. machine gun or a truck mounted AA gun and make a heck of a lot of noise for a while.
Or you could hire a gremlin. With a hammer and a hole punch and do it less obviously.
But nobody reported either actions, noises, or gremlins. and a action like that would leave a lot of evidence, like the spent rounds in the dirt..
There seems to be a desperate desire to show that the US authorities are lying.
First I would point out that they have not been very engaged in this at all, save for the satellite footage and a bunch of blarney so let's take that out and go with what we got from the locals and the European press and reports from the ground by NGO’s.
Seems sufficient to me...pending any news that would turn the entire thing upside down.
There have been sporadic reports of heavy fighting in and around the area where the wreckage came to rest, including combat with IFVs that mount a 30mm cannon. Intentional or not, it is possible for the wreckage to have been shot up by one. (After the aircraft crashed and became wreckage, that is.)