The incident happened in a high-profile part of downtown, and some spectators gathered to watch Saturday afternoon, including Jeremy Beckham, who works for the group People For the Ethical Treatment of Animals, and Amy Meyer, who took video of the horse.
Beckham said Jerry's condition may have been partly caused by colic, but it was aggravated because the horse was being forced to work in near 100-degree temperatures. Highs reached 97 degrees in Salt Lake City on Saturday.
"I don't think horses should be pulling carriages when it's 100 degrees out. That's just inviting problems. Horses get overheated very easily," he said.
Beckham said that it is simply inhumane to have horses pulling carriages in noisy, dirty and hot urban environments.
Under Salt Lake City ordinances, carriage horses are allowed to work unless the heat index the combined temperature and relative humidity reaches 150 degrees, which would require Salt Lake City's record high of 107 degrees, plus 57 percent humidity.
The ordinance also requires water breaks for the horses every two hours and limits how many hours the animals can work in a day and week.
A piece of machinery was brought in to help move the 1,800-pound Jerry out of the roadway and into more comfortable surroundings.
Sunday, his owners and veterinarians were with him, hoping he would recover, Overson said. She placed the odds Sunday at about 50-50 and said the horse was resting as comfortably as possible.
"We're just heartsick right now," Overson said. "We know we're going to be judged by some people. We really are doing our absolute best."
Overson said it is the first time in 27 years that anything like Saturday's incident has occurred.
"We hope it never repeats itself," she said.
Overson said Jerry is one of the best horses they've got and has guided tourist around for about eight years.
"All we can do is keep him medicated and as comfortable as possible," she said.
She said Jerry had exhibited no symptoms prior to Saturday's outing.
"When it hits, it will hit hard," she said of the colic.
She said colic in horses happens, and its symptoms are a lot like that in babies miserable.
Except that while babies have the option to spit up and burp, horses cannot. Horses have to wait for the colic to pass through their rear ends, Overson said.