Las Vegas police shot dead one chimpanzee and tranquilized another after the animals escaped from a back yard and went on a rampage.
According to the Associated Press, the chimps were loose around 30 minutes, pounding on cars and jumping into at least one vehicle.
The male primate, believed to weigh up to 200 pounds, even jumped onto a police car, which had its lights going and an officer inside, a witness told the AP.
"We tried to establish a perimeter until the experts arrived," said Marcus Martin, a Las Vegas police spokesman, told the AP.
"But they couldn't get there in time."
ABC News identified the chimps as Buddy and CJ, local "celebrities" who were put on display every weekend for money.
An officer shot and killed the male, while the female, was shot with tranquilizer darts and returned to her cage.
ABC quoted animal activists Linda Faso as saying the chimp's death provided a tragic lesson in why Nevada needed a ban on people from keeping chimps and other exotic animals.
"It often takes an animal death, or something awful to happen to them, to bring attention to this issue," she said.
"Like in this case, an innocent animal lost its life, another was tranquilized. People shouldn't have these wild animals as pets. As citizens, it is our responsibility to make sure laws change. These animals don't have a voice."
She said the chimps would indeed have presented a threat to humans when on the loose: "Their hands have the strength of five to seven men. They are dangerous and have instincts. You never know if a sound, smell or noise will trigger them."
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