A vigil was held in Cincinnati Monday to mourn the loss of an endangered gorilla.

The gorilla, named Harambe, was shot and killed Saturday after a 4-year-old boy got into the gorilla enclosure at the Cincinnati Zoo and was grabbed by the animal.

Many have turned to social media, saying the zoo should have tranquilized Harambe instead of killing him.

Zoo officials say tranquilizing the gorilla was not an option.

"The gorilla was clearly agitated. The gorilla was clearly disoriented," says Cincinnati Zoo Director Thane Maynard. "And so the idea of waiting to shoot it with a hypodermic was not a good idea. It would definitely create an alarm in the gorilla."