1) Demilitarise the police except for very specific, legally-defined circumstances. We don't need cops running around with body armour and automatic weapons pretending like they're soldiers while they kick in doors of private dwellings.
2) Make the cops actually abide by the Constitution. Get a warrant, and serve the warrant. Don't just bust down doors on a bogus "warrantless entry" action.
3) Corroborate informant information with evidence from other sources. We don't know that's what happened here, but it's often the case that police act on "tips" from people with grudges against the victim, and the cops don't check into it since they're hoping to score a big drug bust so they can get that new department "anti-drug boat" just in time for summer.
If WE are really serious about ending junk like this, we need to stop referring to public servants as "authorities".