The firefighter, in a fit of rage, ripped the hydrant out of the ground with the firehose before starting to put out the flames. Nobody knows how he manages to achieve it. He is moving around to put out fires everywhere now that he is quite mobile. His aim is off and pretty wobbly because of the hydrant he is carrying, which is really hefty. He needs your assistance to extinguish all of the fires on each level. Use your hose to blast each fire out. Be careful, though, since a poor ricochet might easily knock the firefighter out. The explosion can ricochet off of things to put out fires and packs a powerful punch.
To aim, move your finger or the left mouse button while holding it down (on touch-screen devices). When you release, the firehose will spray water at you. Up to a point, the steadiness of the firemen increases as you hold your aim in one place before shooting.