There is more going on here than you are telling us, but you should not say any more. Avvo is not a confidential legal consultation. It is a public internet site which anybody can ready, and which can be monitored by the police. I strongly recommend that you retain a good criminal defense attorney immediately and that you discuss this matter with absolutely nobody under the sun except your lawyer. That means not the police, not the prosecutor, not anybody else who may be under suspicion, not your brother . . . nobody.
A burglary with a firearm, and apparently a shooting, involved? This is very, very serious. Act accordingly.
There are a number of potential crimes at issue here, and anytime a firearm is involved in a felony offense the penalties increase exponentially. If there is any concern there may be criminal liability for you or someone you know, you need to contact an attorney sooner rather than later. Make sure you, or the involved party, do not discuss the specific facts with ANYONE aside from an attorney involved in this case, especially over email or txt message or any other format that can be preserved and used against you or someone else at a later point in time.
Jeff Holmes - Attorney at Law - www.vancouverdefense.com - 360.975.9288. Disclaimer: This answer does not constitute legal advice. This information is based on general principles of law, as well as my general experience that may or may not relate to your specific situation. This information is not meant to take the place of actually consulting an Attorney in your jurisdiction. If you would like legal advice, I would recommend consulting an attorney in your locale.
If the cops get the gun they can match the firing pin location on the casing. Also, bullet casings are very good for fingerprints, since they have to be handled while loading. This is especially true in a gun with a clip.