A safety report about an incident in which a keeper at the National Zoo was seriously injured in a zebra attack says it was the result of human error.
The report, which was released Friday, says the gates and doors were left open between the Grevy's zebra's stall and the adjoining yard where the keeper was working.
It was unclear why they were left open, which was a breach of protocol, the report said. There were no engineering or mechanical failures with the facility or equipment.
The keeper was bitten multiple times Nov. 19 by a 10-year-old Grevy's zebra named Gumu, and had to undergo surgery.
The attack happened inside the zoo's Cheetah Conservation Station, which the National Zoo says is facing serious problems.
"The key finding of our investigation is that animal care and overall organization, accountability, follow-up and communication are severely lacking" in the exhibit area, investigators from the zoo's Institutional Animal Care and Use Committee wrote in a Sept. 3 report.
In Friday's release, zoo officials said staff members and a volunteer keeper aide took "heroic efforts" to rescue the injured keeper by distracting the zebra and moving it to a secure area.
The zoo also said that the injured keeper "acted with clarity during the incident, which likely prevented him from receiving further injuries."
The zebra involved was checked immediately by the veterinary team and has shown no evidence of illness. He is described as an aggressive animal but hasn't shown any unusual behavioral changes, the report said.
The zoo is now conducting its own internal audit of management protocols, it said.
During the incident, a 1-year-old Dama gazelle named Tony died after he ran into a barrier. The zoo says it appears he was spooked and fractured a vertebrae.
The zoo's remaining zebras, 5-year-old Moyo and Domo, are still on exhibit.
Grevy's zebras are an endangered species native to northern Kenya and eastern and southern Ethiopia, according to the National Zoo's website. Grevy's zebras can grow to be nine feet long and five and a half feet tall. They can weigh up to 990 pounds.
The incident happened the same day that the zoo's Sumatran tiger cubs made their public debut.