I had a similar experience when I was younger: when i was a student at University, I was a volunteer stretch bearer for the Red Cross.
One time, we were called to take care of a drunk person. When we arrived, the drunk had just woke up and was feeling decidedly uncooperative... now, we couldn't obviously force him to climb on the ambulance, but leaving him be without him signing a paper where he assumed full responsibility would not have been allowed out of us, we could have had troubles, so we contacted our equivalent of 911 (118, for the curious) and asked instructions.
Shortly after a patrol car of Carabinieri arrived on the spot (one of the 3 police corps we've, it's a military corp and usually don't take care of low-level disturbances, but evidently they were the ones available that evening).
An officer dismounted the car, very calmly watched the situation, advanced up to the drunk yelling man and without warning quickly slapped him two times. Not very strongly, but neither a light tap.
He then quite gently but still very confidently stated "you're going with them".
From what I remember, the officer was not armed. The other officer, younger, that was near the car instead was.
At that point anyway the drunk man, quite surprised and suddenly silent, thought for a moment about it, and answered "I think I'm going with them".
As the drunk man seemed more cooperative, they let us do our things and only followed the ambulance up to the hospital.
Now, i don't think they exactly acted according to protocol, but I've to say that it worked quite well...