In the morgue close-ups, the "dead" victims are clearly breathing.
When the full circumstances of the robbery & murders are shown the shooter walks in and fires two shots; after the second shot the pistol's slide locks open (it clearly wasn't a jam) indicating the magazine is empty, the shooter then proceeds to fire six additional shots. These additional shots aren't shown, but there was not enough time for the shooter to reload; additionally the gun used is a Beretta 92 9x19mm which has a standard magazine capacity of 15 rounds, it shouldn't be empty after just two shots.
After Baylis and Falsone find a gun in Curtis' dresser he denies its his, then Falsone says "so that means we won't find your fingerprints on it then?" and Curtis replies "even if they are you can't use it in court, you ain't got a warrant"; then Falsone sets it on a shelf and says "don't need one, it was in plain sight". However Curtis is on parole which means they don't need a warrant to search him or his residence; when a person is offered parole they are required to sign a form declaring they agree to certain conditions. Those conditions vary depending on what crime they were convicted of but usually include regular visits to their parole officer, being employed, submitting to drug and alcohol tests, therapy, not associating with other felons among others; however one condition all parolees have to agree to is the waving of their Fourth Amendment rights, they and their property can be searched at any time without a warrant provided there is probable cause to believe they violated a condition of their parole.