Investigating a terrible accident

There was a terrible bus accident. Unfortunately, no one survived the accident except a monkey which was on board and there were no witnesses. The police try to investigate further but they get no results. At last, they try to interrogate the monkey. The monkey seems to respond to their questions with gestures. Seeing that, they start asking the questions.

The police chief asks, "What were the people doing on the bus?"

The monkey shakes his head in a condemning manner and starts dancing around; meaning the people were dancing and having fun.

The chief asks, "Yeah, but what else were they doing?".

The monkey uses his hand and takes it to his mouth as if holding a bottle.

The chief says, "Oh! They were drinking, huh??!" The chief continues, "Okay, were they doing anything else?"

The monkey nods his head and moves his mouth back and forth, meaning they were talking.

The chief loses his patience, "If they were having such a great time, who was driving the stupid bus then?"

The monkey cheerfully swings his arms to the sides as if grabbing a wheel.