In the second bizarre incident at the State Fair in a week, Cal Expo police shot an agitated, pregnant dairy cow that twice escaped her confines and knocked over an officer as she bolted through the fairgrounds Tuesday morning.

Neither the cow nor her calf survived the shooting, which occurred an hour before gates opened to the public.

Ultimately, the roughly 1,200-pound cow became a threat to thousands of employees already abuzz in the fairgrounds, police and veterinary officials said. They agreed she had to be put down after a 1 1/2-hour chase.

"Obviously, we're in a caring profession and the last thing we want to do is see an animal euthanized," said W. David Wilson, director of the veterinary medical teaching hospital at the University of California, Davis, which oversaw the care of the cow.

However, he added, "A very difficult choice had to be made."

About 9:30 a.m. Tuesday, UC Davis veterinarians were delivering the cow to the fairgrounds, where she was expected to give birth to her calf before wide-eyed fairgoers as part of the long-standing Livestock Nursery program.

But the cow became agitated and fled, running about 500 yards toward a tunnel connecting to the midway, said Brian May, deputy general manager of the fair.

Police officers and veterinary officials corralled the cow and penned her in with crowd-control barriers, May said.

He added that veterinarians did not want the cow tranquilized because they feared for the calf's health. But they calmed her some by plying her with food and hay, Wilson said.

An hour later, as officials tried to load her into a trailer, she again became anxious and fled.

Getting desperate, veterinarians agreed to tranquilize the cow. Two attempts failed, and the cow again broke loose from another makeshift pen, knocking over an officer in the process.

At that point, May estimated, several thousand of the fair's 10,000 employees already were setting up shop on the grounds. Proud youngsters were nearby, too, caring for their own livestock on display at the fair.

Officers made the decision to shoot the cow, May said. Wilson said the veterinarians reluctantly agreed.

"Very, very rapid" action possibly could have saved the calf's life, but the circumstances were not conducive to such a surgery, Wilson said.

Lafayette resident Jennifer Nelson and her children were inside Cal Expo to promote water conservation when a security guard alerted them about the loose cow.

From a distance, they could see the cow penned in by vehicles. Then she heard shots – which she assured her children were the sounds of tranquilizer guns.

Nelson, who spent her childhood summers showing sheep and rabbits at the fair, later learned they were not. She then tried to reassure her children in a different way.

"I said, 'Whatever happened, it must have been a difficult decision,' " Nelson said. "This is an organization that isn't going to willy-nilly make the decision to kill an animal if they could get the situation under control some other way."

Nevertheless, "it was just a really sad situation," she said.

Wilson said the cow's behavior was not typical of a pregnant cow, and that that particular animal – as all livestock chosen for the nursery program – had been screened for good disposition.

But any domesticated animal has the potential to react violently when threatened, Wilson said. Cows are no exception.

"If they get into a frenzied situation where they want to escape, they will charge fences, they will charge people," Wilson said. "So people can be badly injured or killed even by a cow."

Wilson described the event as "tragic." But he said it did not make him rethink the Livestock Nursery program, which has been a fair staple for decades.

The program helps fairgoers connect with their food sources and the agricultural world, while also inspiring future generations of veterinarians, he said.

Wilson said he does not suspect that the incident stemmed from any missteps in procedure, but added that officials will review those guidelines to look for improvement. Fair officials promised similar reviews.

The Livestock Nursery program is expected to continue through the duration of the fair, which ends Sunday.

Just days earlier, fair officials were fielding media calls after an equally strange incident: Two armed men – possibly employees of a food vendor – walked into a cash-counting room and left with $100,000 in a bag. They haven't been seen since.

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