An entire herd of cattle were swept away from a field where they were pastured in Oklahoma. Heavy floodwaters came after more than 13 inches of rain drenched the area, according to an NBC News affiliate.

A video of the incident taken by bystander Alex Spahn and posted to Twitter shows dozens of bovines being overtaken by a forceful flow of water throughout an area of farmland south of Oklahoma City called Fittstown.

Warning: some readers may find the following video disturbing

Spahn posted a series of short comments to go with his video.

"Terrible! I just watched a herd of cattle get swept away under a bridge in floodwaters just south east of Fittstown.

"For those asking, I am unable to provide an update on the status of the cattle.

"I watched them downstream as far as I could and only saw 3-4 make it out before they disappeared from my view.

"Fingers crossed they all make it out in time."

According to the owner of the cattle, some of them were able to get to land thanks to an airboat rescue (an airboat is a flat-bottomed watercraft propelled by an aircraft-type propeller and powered by an automotive engine), but there are quite a few animals that are still unaccounted for. The owner stated that he has faith that all of them will be recovered safely.

Cows, like most mammals, are natural swimmers. There's plenty of evidence of this stemming from cattle-drives across raging rivers in the Old West. And, more recently, the proof has been posted on YouTube.

Cows prefer to wade in shallow ponds to cool off. When it comes to vigorous swimming in deep, fast-moving flood currents, they are not as adept. Unlike horses who move through the water, cows mostly float and they propel themselves by moving their hooves as if running in a field.

Just prior to the incident involving the cows shown on the video, the National Weather Service issued a flash flood alert for parts of southern Oklahoma after heavy rain continued to deluge the area. The floodwater also caused numerous roads to be closed in southern Oklahoma.

Reaching nearly 13 inches, this was the highest-ever watermark recorded in 25 years since the Oklahoma Climatological Survey's Mesonet was enacted. An area of low pressure over West Texas and Oklahoma, tropical moisture from the Gulf of Mexico, and a cold front were to blame for the unusually heavy rainfall.

There is mild rain expected in Oklahoma throughout the coming week.