How would you dispose of a handgun?
In this movie, somebody chose exactly the wrong way. What method would you use?
Wiped clean and dropped at the bottom of a river.
Never to be found.
That would be why police search every nearby water crossing to a crime scene.
If I had access to a steelworks I would throw it into a ladle of molten steel, thus destroying it and dispersing it through the rest of the steel.
That access is wildly unlikely for me to have.