An elderly Farmersville couple was killed early Tuesday when their home near Lake Lavon burned to the ground. Farmersville police say 86-year-old Delvin Harrison Sergent and his 88-year-old wife Betty Lou were inside their home when it caught fire at about 4:00 am. Their bodies were found after the fire was extinguished. The cause of the blaze is under investigation by the Collin County Fire Marshall.