The Los Angeles Zoo's chimpanzee exhibit was calm inside a private room after an adult male chimpanzee killed the troop's only baby yesterday.
"They're just quiet ... We can't really understand what their thought process is, but we can see they recognize that the baby is dead," L.A. Zoo director John Lewis told The Huffington Post.
Spectators watched late Thursday afternoon as the adult attacked the 3-month-old female, but workers could not intervene because it is not safe.
Lewis added that according to visitor reports, the adult chimp grabbed the baby from her mom, Gracie, "really fast" at around 3:30 p.m. One observer said that the attacker, who was not the father, threw the baby around after snatching her.
The zoo had been introducing the baby chimp gradually into the exhibit, and to some staff the incident came as a surprise.
"All of the interactions have been positive, and the chimps have been curious about the baby, they want to be near it, they want to touch it, and this male too," L.A. Zoo curator of mammals Jennie Becker told KTLA.
Hear Becker describe how zoo staff reacted during the incident and see footage of the baby before it was killed:
Zoo officials apologized for the chimpanzee's unexpected actions, but added that the animals can sometimes exhibit aggressive and violent behavior. Lewis told NBC LA he talked to several visitors to help them process what they had seen.
"I felt bad for the people that saw that happen today. There were young children there that were so sad, you know, it's just really heartbreaking," he said.
The unnamed chimpanzee infant was the first to be born at the L.A. Zoo in 13 years, after a 1999 chimpanzee baby boom. Then, one baby was born and two females impregnated within a month, leading zoo officials to give four of the adult female chimpanzees birth control pills.