The couple, identified as 44-year-old Kristen Beauregard and her boyfriend, were exercising their two miniature horses at their home in Pantego, when the bees appeared out of nowhere and attacked them, Xinhua reported citing the Fort Worth Star-Telegram newspaper.
The woman was stung about 200 times and her boyfriend 50. The two horses were stung so much that they did not survive.
The couple were, however, able to call the emergency number 911 and firefighters arrived with special gear and a foam substance to clear the bees.
The couple were sent to a hospital.
The bee hive was found to be in a shed in the backyard of the couple's rented property and housed an estimated 30,000 bees.
The report said the bees are being tested to find out whether they are "Africanised" bees, also known as "killer bees" for their aggressive behaviour.