Swatting is a crime in a good deal of locations nowadays and a lot of police forces in the US (and likely others) are now well aware of the tactic and will sometimes consider it as a possibility alternative to why they've been dispatched if what they find at the scene varies enough from what would be expected.

Definitely report this, though, if for no other reason than to ensure that the agencies in your area (city, sheriff, possibly others) have a formal report on file to deal with this person threatening to submit a false 911 report against you and ideally cross-referenced with your name and address to ensure 911 calls will display the existence of the threat.