A South African investigator says a witness heard a gunshot at the home of Oscar Pistorius, followed by a woman screaming and more gunshots last Thursday, when the Olympic runner killed his girlfriend, Reeva Steenkamp.

The investigator testified Wednesday in the second day of a bail hearing. Prosecutors say the shooting was premeditated murder, while Pistorius insists he thought he was shooting at a burglar.

The detective said police found one shell casing outside the bathroom where prosecutors say Steenkamp locked herself before the shooting, and three more shell casings inside.

He also said police found testosterone and needles inside the home, which the defense countered was an herbal remedy.

Earlier, prosecutors said a witness overheard an hour of non-stop fighting prior to the shooting. The investigator said the witness was 600 meters away - a distance the defense says is too far to hear.

In the prosecution's account of the shooting, Pistorius put on his prosthetic legs, walked seven meters across his bedroom and shot four times through the door.

Pistorius said in an affidavit presented Tuesday he had "no intention" of killing Steenkamp and he was "deeply in love" with her.

The magistrate ruled that premeditation cannot be excluded in the case, but that the charge could be downgraded later. Pre-meditated murder carries a possible lifetime prison sentence.

Investigators have said Steenkamp was shot by a nine-millimeter pistol registered to Pistorius.

Her family held a private funeral Tuesday in Port Elizabeth, while the hearing was taking place.

Pistorius is regarded as a sports hero and national icon in South Africa. He made history in August when he became the first double amputee to run at the Olympics.

He is known as the "blade runner" for competing on high-tech artificial legs.