“A reasonable person would have looked where Reeva was, if she was safe. You just grabbed your gun,” Nel told Pistorius during cross-examination.
He is accused of murdering model and law graduate Steenkamp in his Pretoria home around 3am on February 14 last year.
He shot her through the locked door of his toilet, saying later he mistook her for an intruder.
Pistorius has said that shortly before the shooting he got out of bed to bring in two fans from his balcony.
Steenkamp apparently got out of bed without him noticing and went to the bathroom. He then heard the bathroom window sliding open, got his gun and went towards the noise.
Nel reminded Pistorius about the evidence of two couples who had heard shouting and shots from Pistorius’s house.
“The Stipps said the first thing that happened between them is they spoke to, each other. ‘Did you hear that?’ The Johnsons spoke to each other, but you didn’t.”
Pistorius replied: “I was not right next to her when I heard the noise. I was on the other side of the bed.”
Nel: “You wanted to arm yourself. That’s the first thing that went through your head.”
Pistorius: “There were many, many, many things that went through my head.”
Pistorius is also charged with three contraventions of the Firearms Control Act, one of illegal possession of ammunition and two of discharging a firearm in public.
He allegedly fired a shot from a Glock pistol under a table at a Johannesburg restaurant in January 2013.
On September 30, 2012 he allegedly shot through the open sunroof of a car with his 9mm pistol while driving with friends in Modderfontein.
Pistorius has denied guilt on all the charges.