Hawaii-based Dolphin Quest has terminated its contract with an Arizona dolphin attraction after last week’s death of an animal that was on loan from its Waikoloa location.

A 22-year-old male Atlantic bottlenose dolphin named Kai died Thursday at Dolphinaris Arizona in Scottsdale near Phoenix. It was the fourth dolphin within two years to die at the park, which allows guests to interact with the marine mammals.

Kai was transferred from Dolphin Quest’s Hawaii island location to Arizona in September 2016 and participated in educational and “experiential learning” programs. The animal’s health began to decline about two weeks ago as it showed signs of difficulty swimming, eating and breathing, according to a post on the Dolphinaris Arizona website.

“Our team made every effort to save his life, including bloodwork testing, ultrasounds, X-rays and engaging external specialists and submitting diagnostic samples to outside university veterinary laboratories,” said General Manager Christian Schaeffer in the statement.

When the dolphin’s condition worsened, “we made the extremely difficult decision to humanely euthanize Kai ensuring he would pass peacefully,” Schaeffer said.

Dolphinaris has hired an external pathologist to conduct a necropsy to determine what caused the dolphin’s death, he said.

Dolphin Quest officials said in a statement Saturday that they were “heartbroken” over the latest dolphin death and formally terminated their animal loan contract with the Arizona facility Friday. The company, which also has locations at the Kahala Hotel &Resort on Oahu and in Bermuda, has two remaining animals in Arizona and is currently deciding on the next steps for them.

“The safety and health of our animals is our top priority,” Dolphin Quest co-founder Rae Stone said in the statement. “In spite of their best efforts, the animal health concerns have not been resolved at Dolphinaris. We have a senior marine mammal specialist from Dolphin Quest on site at Dolphinaris who knows our remaining dolphins well and is closely monitoring them. They are bright, alert and in good condition at this time. We have contacted (the U.S. Department of Agriculture) and are working with them as we move forward.”

The USDA’s Animal and Plant Health Inspection Service told Arizona news outlets Friday that officials are aware of Kai’s death and are “working on the next course of action.” The statement did not specify what that might include.

Meanwhile, over 100 protesters rallied outside Dolphinaris Arizona Saturday, calling for its closure.

“We recognize losing four dolphins over the last year and a half is abnormal,” Schaeffer said. “Over the last several years we have worked with a team of external experts in the fields of animal behavior, water quality and veterinary care to ensure our dolphin family remains healthy. We will be taking proactive measures to increase our collaborative efforts to further ensure our dolphins’ well-being and high quality of life.”