Agent 'X', in his strategic positioning, hadn't accounted for Lenny's ingenuity in using the environment to his advantage. The fireworks, while harmless directly to him due to the game's rules, became a deadly threat when used to ignite the old, dry wooden structure of the house he was using for cover.
As the realization dawned on him, Agent 'X' could only curse his oversight. The rules of the game had made him complacent, focusing only on direct attacks and forgetting the indirect dangers that could arise. The building, now engulfed in flames, quickly became a death trap. The dry wood, a perfect fuel for the fire, made the blaze spread rapidly, consuming everything in its path.