Meagan Hall of Boise and her son Theo dropped off a homemade sympathy card at the zoo.
"We just wanted to bring it in to express our sadness to the zoo about the poor monkey," said Hall.Around four-thirty early Saturday morning, a security guard at the zoo spotted two males in dark clothing, one inside the 8-foot zoo fence, another outside.
When police and zookeepers responded the suspects had fled.
But the fatally injured monkey, taken somehow from an enclosed exhibit, was found just inside the perimeter fence.
The animal was rushed to an onsite hospital and the zoo's vet.
"He was still alive and groaning," said Zoo Boise Director Steve Burns. "But when we took him to the hospital and got him out of the crate (the veterinarian) said he had died."
An autopsy ruled the cause of death as blunt force trauma.
Police are analyzing blood samples found at the scene.
"In the 96-year history of Zoo Boise, something like this has unfortunately happened at least once before that we know of. in the late 1970s, somebody broke into the zoo and fatally poisoned a tiger."
Now, the zoo is concerned about the future of the lone surviving Patas monkey.
Primates are social animals and this Patas needs company.
"They're not that common in zoos around the United States," said Burns. "So we're not sure if we can fInd one or not, if we can't find one we may need to ship this monkey to another zoo so it can be with other Patas monkeys."