PRETORIA, South Africa (AP) — A former girlfriend of Oscar Pistorius has testified at the double-amputee runner's murder trial that their relationship ended when he cheated on her with Reeva Steenkamp, the woman he fatally shot last year.

Samantha Taylor also testified today that Pistorius carried a gun with him "all the time" when they were dating, and on one occasion he fired it out of a car's sunroof soon after a policeman stopped the car they were in for speeding.

Pistorius says he killed Steenkamp in his home by mistake, thinking she was an intruder. Prosecutors say he intentionally killed her after an argument.