obsessed maniac

You found yourself in a maniac's lair, and your escape route took you into a ventilation tunnel. You crawled forward as fast as you could, taking random turns. You didn't know where you were going, but you kept moving, turning in different directions. But on one turn, you made a mistake...
At the next turn, you turned left and looked through the bars and saw him. At first, you couldn't tell if he was coming toward you, so you froze to avoid making any noise, but he came right up to the bars and started ripping out nails with a crowbar. You abruptly darted forward, and despite trying to back away, you flew as fast as you could, but because you were trying to run faster, you were moving incorrectly, bruising your knees with every step, making it painful to move forward, and you slowed down. He was already approaching you from behind, moving quickly and nimbly, looking like he was practicing the Army's "soldier run." Ultimately, your tired, painful, and pathetic escape ended in failure. He caught up with you and grabbed you from behind (what he'll do to you is up to you to write. And now I look back at what I wrote, and it seems to me that it all looks as if I've lived it myself...)