I don't KNOW but doubt they had a chop saw in a Dick's stockroom somewhere.
There are companies that contract demil of guns either confiscated or surplused and too dangerous to allow "back on the street."
One such outfit has a machine like a log chipper for metals that reduces the guns to fragments of scrap metal.
Another neatly sections the receiver, apparently by bandsaw, leaving nice "parts sets" for resale.