It's one of the hardest, but necessary aspects of running an animal shelter.
And starting Saturday, the staff at the Humane Society of Northeast Texas had to put down 154 dogs who showed signs of distemper which is an incurable, airborne disease that only affects dogs.
Distemper attacks the animal's respiratory and central nervous system, causing seizures.
And it can be a long painful death.
The humane society tells Fox 51 the initial distemper case did not start in their facilities, but a dog who was brought in had already contracted distemper .
And some who have worked with the shelter understand the tough decision the humane society had to make.
Officials tell Fox 51 that resorting to euthanizing dogs with distemper is standard operating procedure.