Pretoria, South Africa (CNN) -- Did Oscar Pistorius have time to think before he shot and killed his girlfriend Reeva Steenkamp last year? That's the question that state prosecutor Gerrie Nel dug into Thursday with a doctor who has spent years working with the disabled athlete. "His intention was to shoot, whoever he came across -- if he came across anyone" in his home on a February night last year, Nel put to the doctor, Wayne Derman. "I suppose if he came across an intruder or danger, he would shoot," Derman responded. And Pistorius was firing to kill, the prosecutor said.
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NEW: Oscar Pistorius was shooting to kill, the prosecution argues at his murder trial
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Pistorius' defense team highlights his disability and vulnerabilities
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The athlete is accused of deliberately shooting his girlfriend, Reeva Steenkamp
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He says he shot Steenkamp accidentally in his bathroom, mistaking her for an intruder
Gerrie Nel
Nel
Exchanges between the two got testy, with @placeholder trying to get the doctor to explain Pistorius' actions moment by moment on the night he killed Steenkamp.
Wayne Derman
Derman
@placeholder grew irritated with Nel when the prosecutor responded: "That's not true" to a statement Derman gave, and he appealed to the judge that Nel was being "unprofessional."
Gerrie Nel
Nel
Derman grew irritated with Nel when the prosecutor responded: "That's not true" to a statement Derman gave, and he appealed to the judge that @placeholder was being "unprofessional."
Oscar Pistorius
Pistorius
Oscar Pistorius
Pistorius
"When Mr. @placeholder's appraisal of the situation is that he might be physically threatened, a fear response follows that might seem extraordinary when viewed from the perspective of a normal bodied person, but normal in the context of a disabled person with his history," the doctors found.