Johan Stipp, a neighbor, testified he saw the body of a woman on the floor in Pistorius' home in Pretoria on Feb. 14, 2013, and heard a man kneeling next to the body saying "I shot her," the South African Broadcasting Corp. reported.
Stipp, a physician, told the court he heard screams and three loud bangs he thought were gunshots, and that he went over to the house to offer medical assistance.
Prosecutors maintain Pistorius, a double amputee, deliberately killed his girlfriend, model Reeva Steenskamp, when he fired a gun into a closed bathroom door. The defense says Pistorius thought he was shooting at an intruder who was hiding in the bathroom.
During cross-examination, defense attorney Barry Roux suggested that an anxious and distressed Pistorius could have been the one Stipp heard screaming, rather than the screams of a woman, Britain's the Guardian reported.
Roux and Prosecutor Gerrie Nel argued whether Stipp heard shots both before and after he heard screams. Roux has maintained that Steenkamp was too fatally wounded to make such loud screams.
Also Thursday, Roux asked prosecution witness Charl Johnson about the discrepancies between his first and second recounting of events when Steenkamp was killed. Roux has suggested sounds Johnson heard weren't gunshots but were from a cricket bat Pistorius used to break down his bathroom door.
The trial will resume Friday.