Unknown water damage, who's liable?

Recently I sublet a room. One day the landlord put a note on the door saying there's water leakage from our apt floor and caused damage to downstairs. But when that happened no one was in the apt.

Then I tried to contact the landlord he's been very difficult to reach. About 2/3 weeks later I managed to call him and discussed the incidence.

he's charging $6xx for repainting the ceiling and changing the carpet and compensating the tenant downstairs. I asked him to show me the damages but he said it's already repaired and nothing to show. I asked how did the leakage happen and he claimed may be the window was not fully shut and some water flooded in from raining.

Then I discovered the company that fixed the damage is also owned by the landlord.

My Q: who's liable? Shall I pay the charge?