BRIBES AND UNPROFESSIONAL

Yesterday in the morning I purchased a ticket for my husband to fly to Harare from EBB Uganda. I bought the ticket at 8:25am. Around 8:32 just 7 minutes after making the purchase, I got a message informing me the flight was boarding of which my husband was already at the Airport making his way to the boarding terminal. Only to get there and be informed that the gate was closed. He rushed to the Kenyan Airways offices at the same airport and found another 5 passengers who were being escorted to board the same flight and joined them only to be told by the Kenyan Airways agents at the boarding gate that he couldn't proceed and told to pay something (bribe). My question is why did Kenyan Airways sell a ticket of a flight when they knew the boarding gate for the flight was closing in 10 minutes. Why was my husband refused entry into the flight while other 4 passengers were permitted in. I am so disappointed by this unprofessional service and even after getting in touch with their customer service they insisted we pay extra money for another ticket.