Landlord next door says my roof causes his roof damage

[Nicole A.]

Recently, the owner/landlord of the duplex next to mine reached out to me. He informed me that he recently did repairs to his roof and that apparently two roofers said that the pitch of my roof is channeling a large amount of rain water onto his roof.

Most of the roofs on these buildings are flat, including his. At some point in time before I purchased my property, the roof was modified to be pitched. Both my building and the one next to it had the same previous owner.

I've included the pictures he sent, which is just a view from the ground. I was expecting/hoping for photos of the actual apparent problem from the roof.

I don't know much about roofs, but even if they are flat, shouldn't they be graded to send water away so it doesn't pool? Also, it seems that there is a gutter at the end of the pitch, which would send water away.

Am I responsible for this? He hasn't directly said what he wants yet, but I think it's a bit unreasonable if he is asking me to change my roof back to flat. He didn't seem to notice any of this a year ago when he purchased.