ALTERNATE VERSION: The screams the prosecution claims were heard by eyewitnesses were after the first set of bangs-- the bat striking the toilet door after he had chased Reeva from the bedroom screaming "Get the Fukk out of My House" and she retreated into the locked toilet cubicle. Reeva knows she is in mortal danger and is screaming for her life. Oscar retrieves his pistol and fires 4X into the toilet door, silencing Reeva's screams. Oscar picks up the bat he has thrown aside (possibly damaging the bathtub cover plate) and uses it to pry open the toilet door panels gaining access to the key and opens the door. He sits with Reeva while she takes her last breath and it sinks in what he has done. His first thought is to make it appear to have been an intruder that he mistakenly shot. He runs to the balcony window and yells "Help, Help, Help!" before he returns to the bathroom and drags Reeva out of the toilet, calls Stander, Security, and Netcare. He carries her downstairs and is crying loudly in front of Dr. Stipp, the Standers and Baba from Security who arrive almost immediately.
I think most earwitnesses heard the three helps before the final set of bangs.