According to The BBC, a zoo chimp planed his stone attack. The report goes on to state,
“There has been scant evidence in previous research that animals can plan for future events.
Crucial to the current study is the fact that Santino, a chimpanzee at the zoo in the city north of Stockholm, collected the stones in a calm state, prior to the zoo opening in the morning.
The launching of the stones occurred hours later – during dominance displays to zoo visitors – with Santino in an “agitated” state.
This suggests that Santino was anticipating a future mental state – an ability that has been difficult to definitively prove in animals, according to Mathias Osvath, a cognitive scientist from Lund University in Sweden and author of the new research.”
Seriously don’t mess with the chimps.