Unnecessary proximity

Prologue

Boom Boom Boom!!! A dull sound is heard throughout the apartment, absolutely random and not monotonous. Each blow is invariably loud, sharp, as if someone were hitting right behind the back. Either more often, now less often, he breaks the almost complete silence, in which only occasionally quiet, hysterical sobs are heard.
Boom Boom Boom!!! The further, the more he hits the nerves stretched to the limit. The sound is persistent, continuous, like an endless annoying renovation behind a wall. But in the neighboring apartments, most likely, there is no one alive.
Boom Boom Boom!!! Someone knocks, pounds on the door, with every sound the door trembles, but it holds on ... as long as it holds on. He presses his back to her, but almost does not move and does not flinch from impacts on the wooden surface. The bitten lips are tightly compressed, and the emotionless empty gaze rests on his own knees, almost pressed to his chest.
Boom Boom Boom! The palms are so tightly pressed to the ears that the hands tremble from overexertion. After another blow, there is silence again, but this time it is delayed. And without the usual frightening knock, it becomes uncomfortable, almost tangible, like a thick enveloping jelly. It seems to penetrate the ears, reaches the brain itself, pulls the nerves to the limit. And then, like a dull knife, a new sound cuts through the silence, grinding and uneven, like the surface of sandpaper. The pupils of the brown eyes widen, and the gaze rests on the door. There is no more silence, only a constant repetitive scratching sound, as if someone's claws are sliding along the smooth surface of the door. He flinches as the door strikes resume with the same tenacity and force.
Boom Boom Boom!!! ... and a barely audible hysterical sob sinks again in a series of muffled sounds ...