[...]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.[...]
Santino was observed gently knocking on the "boulders", hitting harder to detach bits that were loosened and adding those to his stashes of ammunition.

I love how they extract every bit of information from this case, EXCEPT that Santino wants them to leave him the fuck alone! Seriously. He'll hit you in the face with a rock, even.