The murder trail of Oscar Pistorius escalated on Friday with testimonies of a security guard, and Pistorius's ex-girlfriend.

When guard supervisor Pieter Baba called Pistorius's home after reports of gunshots going off, the former Olympic sprinter reassured them that everything was fine. Yet Baba was suspicious, as Pistorius was crying. Soon after, they witnessed Pistorius carrying his dead girlfriend's body down the stairs.

"I was so shocked, I couldn't think for a few moments," said Baba during his testimony.

Oscar Pistorius was charged with murder following the death of his model girlfriend, Reeva Steenkamp. The amputee athlete claimed that he had thought his girlfriend was a burglar when he fired his gun four times through the locked bathroom door. Yet, Pistorius's version of events is complicated by the testimony of Michele Burger, who recalled hearing a woman's screams before gunshots rang out from the Pistorius home.

Pistorius' ex-girlfriend, Samantha Taylor, testified Friday that her former boyfriend was very fond of guns.

According to Taylor, Pistorius would carry his pistol every here he went, even sleeping with it at his bedside. He also took the gun out to social gatherings and would place it in the backseat when driving.

Pistorius also had a bad temper, Taylor alleges. He would often go off on her or her friends. There was one incident in which Taylor and his friend were stopped by police and Pistorius got so angry he fired a bullet through the sunroof.

"It was a very, very loud noise," Taylor said. "From my observation, he was angry after being stopped. Thereafter, after firing the shots, [Pistorius and his friend] laughed. They found it funny."

Taylor also alleges that Pistorius was unfaithful during their relationship. The couple broke up multiple times due to his cheating. Taylor finally called it quits for good when he cheated on her with Reeva Steenkamp.

Pistorius is facing a charge of premeditated murder, along with additional charges for illegal possession. If convicted, he may serve a mandatory life sentence.