Conner Sessions’s decision to combine his love of science and animals nearly destroyed him. Growing up in rural Washington state, he spent his early life surrounded by cows, horses, cats, and dogs. He cared about all of them and considered a career in veterinary medicine. But after graduating with a bachelor’s degree in biochemistry from the University of Washington (UW), Seattle, in 2016, he saw a job ad that changed his mind.

The school needed an animal technician, someone to clean and feed mice, pigs, dogs, and other creatures used in biomedical research. “I wanted to get involved with science, and working with animals was a big plus,” Sessions says. He took the job, spending his shifts feeding and playing with dogs and livestock at the university, an echo of his youth. The sheep would head-butt him for snacks.

Sessions grew especially attached to the dogs, which was tough: Some were bred for two different forms of muscular dystrophy, one 100% fatal. He raised the puppies from birth, sometimes tube feeding those that had trouble nursing. “I trained one litter to line up in their kennel for treats,” he says. Then he would walk in one morning and find some of them dead in their enclosures—victims of their disease.

Over the next few years, Sessions came to expect this. But it never got easier. Every time he entered the underground facility where the animals were kept, he panicked, fearful of what he might find. He became anxious and depressed, and began obsessively checking on the dogs throughout the day, a feeling that followed him home. “I’d be doing the dishes at 8 at night and wondering, ‘Should I go back and check if my animals are OK?’” He hesitated to go on vacation or even take weekends off, worried one of the dogs would die or be euthanized while he was away. “I wanted to be there for them,” he says. “It’s almost like they become your pets.”