Dallas Zoo officials said they can’t explain how a 300-pound gorilla escaped from his enclosure, injuring four people before he was shot to death.

Police evacuated an estimated 300 people from the zoo compound Thursday and killed Jabari, a 13-year-old male western lowland gorilla, after he charged at officers.

Zoo workers armed with tranquilizer guns had pursued the animal through the forested jungles of the Wilds of Africa exhibit for about 40 minutes, but could not gain a clear shot, officials said.

“It tried to charge two of our officers, so we had to shoot it,” Deputy Police Chief Daniel Garcia said. “You can imagine the pandemonium we had out here when he got loose. We felt terrible we had to put this animal down.”

'He has my son in his mouth'

The injured included a mother and her toddler son. Rivers Noah, 3, was in fair condition at Children’s Medical Center with multiple bites to his head and chest. His mother, Keisha Heard, 26, who was bitten on the legs, and Cheryl Reichert, who suffered arm injuries, were treated at hospitals and released.

“I was like, ’This is not happening, this is so unreal,’ cause he just came out of nowhere,” Heard said Friday on NBC’s Today show. “I’m watching this gorilla. He has my son in his mouth, he’s attacking him, and I tried to help him and there wasn’t really anything that I could do. ... He slings me back across the concrete area where we are. So it was really scary.”

The fourth injured person, a child, was treated at the scene.

Jabari was in the award-winning gorilla-conservation area, two acres surrounded by a 16-foot concave wall, before the attack around 5 p.m. Some youths had reportedly teased Jabari shortly before.

“He had to have scaled the wall,” said zoo director Rich Buickerood. But “this habitat is among the best in the country. This blows our minds.”

He said he did not know why zoo employees, who were armed with pepper spray, did not use it on the gorilla.

Running for cover

Some zoo-goers hid inside a restaurant and the monorail surrounding the Wilds of Africa exhibit.

The gorilla darted in and out of thick bamboo and trees before officers spotted him on a nature trail. He was holding a pair of white children’s sandals when he came within 15 feet of two officers who shot him, police Lt. Anthony Williams said.

The 114-year-old zoo has been in financial straits and the nonprofit Dallas Zoological Society recently proposed a county takeover. Buickerood said last month that the zoo staff had been cut and maintenance postponed because of the fund shortage.

In 1998, a zookeeper was injured by a 340-pound gorilla after a cage door was left open. The zookeeper suffered more than 30 puncture wounds. That animal was captured with a tranquilizer dart.

Zoo officials said the Wilds of Africa section and the Monorail Safari were closed Friday, but would reopen Saturday.