When you're going to shoot into someone's apartment to try to dissuade them from testifying against you, don't try to manufacture an alibi by conveniently calling a police detective at the exact time of the shooting telling him that you're somewhere else. It'll just sound fishy. It won't work.
But if you ignore my advice and do it anyway, definitely don't use your cell phone to do it. Because they have these things called cell phone towers that know roughly where you called from. And if you claim to be located at X but you're in fact at Y, we'll know you're lying. And if Y, as here, just so happens to be very near the scene of the shooting -- well, you'll have many additional years in prison to think about doing a better job covering your tracks next time.