When Oscar Pistorius gunned down girlfriend Reeva Steenkamp, she began screaming -- presumably in pain and horror -- and he continued shooting ... this according to a prosecution witness.
As the bail hearing resumed Wednesday, prosecutors revealed a statement from a witness who claims he heard gunshots, went to his balcony and saw the light was on. He then heard a female screaming two or three times ... then more gunshots.
If true ... it's devastating for Pistorius, who claims the room was pitch black when he began firing, never realizing he was shooting at his girlfriend. If the lights were on and he heard Steenkamp's screams but kept on shooting -- it blows his intruder defense sky high.
Prosecutors also say they have a witness who says there was "non-stop talking like fighting" between 2 and 3 AM ... shortly before the shooting. Pistorius claims there was no argument before the killing.
And there's this ... the first officer to arrive at the scene says when he got there, a lawyer and Pistorius' brother were already present.
An officer testified the bullets were "fired down," which contradicts Pistorius' story that he was not wearing his prosthetic legs when he began shooting.