OP, you accidentally paid this account TWICE. He did pay 2x 1 BTC, but the second time doesn't show up as paid yet. Make sure you don't pay it a 3rd time!

https://blockchain.info/nl/tx/6c52ab7af56453487bb4adfe2498a896a6236b1535f8be7517ee3bf37bd847f9
https://blockchain.info/nl/tx/f20ef901ab7b6b24cfa316390dc971e950e3c93b32178061140ccc18986ee8f9
https://blockchain.info/nl/address/1KT5DeHHpCxK6ZcgzHkB64EsBL5w6J9A3D