Oscar Pistorius shot his gun out of a car sunroof after an angry exchange of words with a police officer, ex-girlfriend Samantha Taylor revealed in court on Friday.
The Olympic and Paralympic star is standing trial accused of the premeditated murder of girlfriend Reeva Steenkamp with the trial entering its fifth day. Mr Pistorius denies the charge and also denied shooting from his car.
Testifying in the Pretoria High Court, Ms Taylor described Pistorius as a man who could get very angry and claimed he had twice been unfaithful during their relationship, with the second affair involving Ms Steenkamp.
Mr Pistorius' defence team showed the court emails that were said to prove that the relationship with Ms Taylor was over by the time he was dating Ms Steenkamp, but she countered that the relationship was not "officially" over.
In a gripping testimony, she alleged that Pistorius had fired from an open sunroof after growing frustrated with a police officer, who had pulled them over before emptying the magazine of his gun onto the car floor.
She later admitted that PIstorius was laughing around the time he shot the gun.
Ms Taylor also testified that the double amputee kept his gun "on him all the time" and revealed that, while together, Mr Pistorius regularly believed there were intruders in the house at night.
She said it had happened at least twice during their relationship, saying he would wake her up before taking his gun to check.
Mr Pistorius claimed he shot Ms Steenkamp after mistaking her for an intruder.
The calling of Ms Taylor as a witness is to provide evidence for a lesser firearm charge but her testimony provides the prosecution with fodder for the murder charge too as it paints a growing picture of Pistorius as a reckless gun owner.
The fifth day of the trial reached its climax with a testimony from Pieter Baba, a security guard working at Oscar Pistorius' gated community, who followed Ms Taylor on the stand.
He claimed the athlete had told him "everything was fine" when he called to investigate reports of a gunshots on the night Ms Steenkamp was killed by Mr Pistorius.
Mr Baba later revealed that Mr PIstorius called back, crying but refusing to say anything before the line went dead.
If found guilty, the Paralympic gold medal winner could face life in prison.
The trial has now been adjourned until Monday morning.