“You reasonably thought an intruder came through your window, walked into the toilet and closed the door?” prosecutor Gerrie Nel asked him in the High Court in Pretoria.
Pistorius replied: “I’m not sure what an intruder would do if he was caught off guard.”
He has been charged with murdering his girlfriend Reeva Steenkamp in his Pretoria home shortly after 3am on February 14 last year.
The athlete shot her through the locked door of his toilet, apparently thinking she was an intruder about to come out and attack him.
Pistorius said 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.
Pistorius heard the bathroom window sliding open, got his gun and went towards the noise.
He then heard the toilet door slam shut. After he peered into the bathroom and seeing nobody there, he thought the intruder was in the cubicle.
“It is so far-fetched… it’s improbable,” said Nel.
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.