"Advice" like this will definitely go a long way towards making a difficult situation into one you won't recover from. Now, if you just shot a 14 year-old after he egged your house, yes, I'd advise you to shut up and wait for an attorney. You're in big trouble anyway, so don't make it worse. There's a BIG difference in that scenario, though, and one where you just shot someone trying to jack you at gunpoint in the Albertson's parking lot. Saying the cops "aren't your friends" and will immediately "use everything you say against you" is misinformed and, well, stupid.
No, the cops aren't there to be your buddies. They're there to solve the crime. But they have no interest in putting a case on an innocent person. If you shut up, you inhibit the investigation, which will be noted, and do yourself a grave disservice. You need to tell the responding uniforms what happened; this is not screwing yourself over. Be assured, if there are any witnesses, they'll be telling the cops what happened. I'd prefer to have my own version out there. If the suspect you shot has any friends, they'll be putting out their version, too. And you need to tell the cops if any of the suspect's friends got away, where they went and if they were armed. This is a safety statement and allows the responding units to fan out and look for additional suspects. You need to talk to the cops. Now, no one is saying to spill your guts, make judgement calls on your tactics or incriminate yourself. If you're given a Miranda warning, shut and wait for a lawyer. You're a suspect in a possible murder.
You will be transported to the station to await the investigating detectives, who will first go to the crime scene to do a walk-through and interview witnesses. They will then interview you at the station. What you say will confirm what they now already know. Most shootings are pretty easy to figure out to a veteran detective. They understand that there will be differences in what happened; it occurs in every shooting. For instance, number of shots fired. If you're not sure, say so. You need to get your version out there. If you're quiet, you're slowing the investigation and irritating the detective who recommends whether to file charges or not to the DA. Not admitting you shot someone, when it was a self-defense killing, is not helpful. Someone is dead in your living room, who else shot him? He obviously wasn't supposed to be there. A GSR (gunshot residue) test is going to be done, anyway. Everyone here thinks an attorney is your saviour; most lawyers don't have a clue about what happens in a gunfight or how an investigation is run. You want to wait several hours or days in jail to speak with an attorney, fine. But it's a dumb idea if you want to clear yourself quickly and go home.
I investigated numerous shootings in a big city; it doesn't go down like the armchair experts here think it does. If you carry a gun, then do your research in your state. Learn what happens in a homicide investigation. Everyone here wants to know how to handle a shooting situation; better to plan how to handle the post-shooting. There are worse things than killing someone; killing someone and going to jail is one. If you can't control yourself after a stressful incident, then maybe you shouldn't be carrying a gun. Think about your responses to the police; clamming up immediately is not a good plan. And that's from a cop that did this for a living. My advice, based on over 24 years in a big city where shootings are a common, daily occurance. Don't be stupid; think, plan, do your homework, rehearse and consider carefully what you'll say.
Bob