First and foremost - I'm not a lawyer and don't play one on TV.
When the PD does their investigation, they want to establish the relative truth of your statements and the facts that can be uncovered. They'll want to know if and/or how you knew the suspect, if anyone else is/was in the house or with the suspect plus a whole bunch more. This is what you pay a lawyer to help you with... which questions are okay to answer and which ones are "fishing expeditions".
Police asking if you have other guns in the house is pretty much a fishing expedition. Asking if you have guns of
the same caliber in the house may be prudent as part of the investigation.
Police will probably look into every room for any other witnesses. If children are in the house they will want to see that they are taken care of properly (or later interviewed as a auditory witness).
Now... in some places, if your house is neat & tidy on average the cops are likely to take your word for a lot of things. On the other hand, if there are half a dozen gun magazines laying around, plus catalogs from Brownell's, Midway and Cabelas along with ammo boxes, empty magazines and holsters, etc. The cops might think "Hoo boy! We got us a
Rambo here." It would not strike me as unusual for someone to decide to "charge" you, even if they can't make it stick through an arraingment, just so they can confiscate oodles of guns and check them out (see if they're stolen). Once seized, as long as the DA keeps the case open, they keep the guns.
In truth, they should confiscate the fired gun as evidence and use it to match against any recoverable projectile to establish it as
the weapon used. The Coroner establishes the cause of death and perhaps which bullet was the lethal one. The ballistics lab matches the bullet to your firearm, you're okay. If they can't match it to your gun (presuming the slug is useable), then questions come up and you can expect warrants and lots of legal fees. Presuming there are no unexplained bits of evidence and no question about self-defense, they may close the case. In some places the DA must present to a Grand Jury to dismiss the case or refer it for prosecution (i.e. Texas).
Some thoughts
Presuming police don't take all of your guns right away:
Once released, if you have "prized guns" in your collection, especially unique or irreplaceable guns, you might work with a friend or family member to move them
discretely to a safety deposit box in his name or some other secure location.
If someone else will store your gun(s) tell them not to store them with their own guns. Use a separate safe. If police show up with a warrant, it's best to surrender the gun rather than have them tear the place apart.
If you have multiple models of the same gun or similar guns, expect police to figure that out and they may bring a warrant. Your lawyer may advise you go ahead and keep it in the house and turn it over without issue. Personally, I'd switch to a distinctly different caliber/cartridge for a backup gun if possible.
If police do seize all of your guns;
- Tell your lawyer immediately.
- Give him a list of "historical" guns or "irreplaceable" guns (the M1 Garand you traced to Iwo Jima, or your grandfather's Browning 20-gauge; that gun engraved to "Chuck Heston" from Duke Wayne
or whatever.)
- Ask him to immediately notify the PD that specific guns are historical, highly valued or have irreplaceable sentimental meaning beyond monetary value and should not be destroyed. Ask him to issue notice to the court too, especially of any potential historical or "museum pieces".
- Your lawyer might request the PD secure such evidence in a higher security area (like they do for cash, jewels, etc.)
- Ask your lawyer to attempt to release non-suspected guns to him for storage with an FFL or in a secure location under his control. Sort of an escrow arrangement.
If a PD destroys your guns as noted in one of the above posts after being notified of their rarity, irreplaceable value or sentimental attachment, this can be used in a civil-rights lawsuit as a "taking" under the 5th Amendment, even if the PD pays you full appraisal value for each (they've taken future appreciation away from you).
- If Danny Dirtbag's friends or family are making any contact at all, advise both the authorities and your lawyer. Even if you don't know who it is, make the report and get it documented. This includes phone calls.