JACKSONVILLE, Fla. -- An animal keeper at the Jacksonville Zoo and Gardens was rushed to the hospital Wednesday morning with serious injuries after she was gored by a large antelope, zoo officials said.

A male bongo, a horned 600-pound animal from East Africa, attacked Amanda Brown about 10:15 a.m. as she was cleaning the enclosure. She was able to get herself out of the animal's pen and use her radio to call for help.

Brown was taken to Shands-Jacksonville Medical Center with injuries to her neck and leg. Late Wednesday she was reported to be in serious condition.

"This is the worst call a zoo director can get," Executive Director Dennis Pate said.

Officials said that bongos are endangered animals and this animal arrived at the zoo in May. While bongos are normally docile creatures, this particular male had shown aggressive tendencies over the past few months.

The zoo's executive director said they will look into why the animal was not locked up while the pen was being cleaned.

"In this particular case, standard procedure is to lock him in the barn," Pate told Channel 4's Diane Cho. "So our first question is, why wasn't he locked in the barn?"

Investigators said no zoo employees saw the attack, so they are talking to all visitors hoping that someone witnessed it. Pate said the animal is still in the enclosure and zoo officials will not decide what to do with him until their investigation is complete.

Brown has worked in zoos for about five years and was hired at the Jacksonville Zoo last year.

Pate said another zoo employee was hurt last year trying to move a young giraffe.