"No pictures taken; no questions asked", regarding who turned in the gun to the police-run collection point being the relevant point of interest here.
Got an annoying neighbor or co-worker? Ex-spouse working you over in the courts? You get the idea, I'm sure; here's your chance to be a criminal mastermind with the Seattle PD's willing assistance!
Some effort on your part will be necessary of course (it's strategy, not socialist economic policy). There's the whole delicate issue of timing to be considered, not to mention the basic premise of there being no direct witness to the act (and if you can't arrange matters thus and so, the word you want is "fantasy" not strategy), but if killing someone and getting away with it is an as-yet un-crossed off entry on your personal bucket list, then January 23 - 25 next in Seattle, Washington is your destination of choice.
Wash well after the fact, present your anonymous self to a collection point with a well-wiped down (and unloaded) gun the morning of the 26th January, and the evidence vanishes into the police supervised smelter directly thereafter.
Celebrate your success by giving the gift card to some
Strategy works. It works in pretty much direct correlation to the degree of minimal intellect and attention span you can bring to any outcome you work to achieve. To stretch a metaphor only slightly; tools are often not up to the task to which they are put ... and whose fault is that? Getting a Seattle (or virtually any other, really) politician to admit to their strategic mistakes, however, is a matter for another post entirely.
All you proto-Dexters rejoice and start planning your itinerary.