People are used to celebrating gender reveal parties for their friends and family, but many are are unprepared when it’s a complete surprise.

Zookeepers at the Ohio Columbus Zoo and Aquarium were caught off guard Thursday when the gorilla they thought was a male, all of sudden started giving birth.

This led to two discoveries: the gorilla was female and a newborn infant!

Many wondered, “How could the zoo not know about either of these?”

According to zoo officials, veterinarians took a “hands-off approach” when caring for Sully, the gorilla. Upon entering the zoo, she was identified as a male.

Zookeepers admit since Sully was in good health and didn’t need any medical interventions, they didn’t have to inspect her too closely.

This allowed the gender to get misinterpreted.

The zoo also clarified it’s hard to tell gender difference between younger gorillas until they reach age 8.

So far, zookeepers say Sully’s infant is healthy and a girl. They also confirm a DNA test is scheduled to determine the father.