Note: These side activities will give you good karma. You can make them respawn instantly if you save your game, then load the save you just made. Go back to the spot where you saw them and they will be back there again.
These events occur at random locations on the map, the guys are only found in the southern part of the city, you cannot find them on the northern half. They are marked on the mini-map by a blue circle with a rectangle in the middle of it. In game, they are lying on the floor with a bunch of civilians kicking and shouting at them. All you have to do is go up to the prisoner on the floor, and press to heal them. Repeat 10 times for the trophy.