DALLAS -- Several visitors to the Dallas Zoo are recovering Friday after being attacked by an escaped gorilla Thursday.

Investigators are trying to determine how the 300-pound primate -- named Jabari -- broke out of its cage at the Dallas Zoo -- injuring four people, including a toddler.

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Dallas Zoo Patrons Describe Attack

Police evacuated about 300 people from the zoo Thursday and then fatally shot the gorilla after it charged at officers. The animal had been in the zoo's award-winning gorilla-conservation area, which is surrounded by a 16-foot concave wall.

Dallas Deputy Police Chief Daniel Garcia said the people were bitten and scratched.

The injured include a mother and her 3-year-old son. The boy was upgraded from critical to fair condition Friday morning with multiple bites to his head and chest .

Police said the boy's mother is in good condition after the gorilla bit her on the legs and threw her and the toddler against the wall

Another woman who shielded several children from the gorilla suffered arm injuries and is in good condition. The fourth injured person -- a child -- was treated at the scene.

Some youths had reportedly teased the gorilla shortly before the escape. The zoo's director says the escape "blows our minds."

"We were forced to put this animal down," Garcia said.

Garcia said the police officers' objective was protecting citizens until authorities could figure out what to do with the gorilla.

"I'm sure that there's a lot of people out here that were very shook up by the fact that you had a huge gorilla running through the premises like that," Garcia said.

According to officials, the situation was too risky to attempt tranquilizing the gorilla.

Diana Gonzalez, a zoo patron, said she saw the gorilla banging on the door of its enclosure, and then it broke. The gorilla then scampered out of the gorilla pit.

Dallas zoo director Rich Buickerood said the primate was an inquisitive 13-year-old western lowland gorilla. He said the animal was likely "extremely excited and extremely fearful while it was out."

He said zoo officials are trying to figure out how the escape happened.

The zoo remained closed and locked down Thursday evening.