Shadow people (plural) or some called the shadow man (they are huge shadows and sport dark top hats or fedoras with dark flowing capes.)

Legends of the Shadow beings have been told by the Mississippi Choctaw indigenous tribes to parapsychologists. Urban legends of shadow men are discussed on alien TV series and radio. 

Sketch of Shadow people in Public Domain, unknown artist

Who or what are the Shadow People? A shadow person or people whom are the perception of patches of shadows as living, humanoid figures, particularly as interpreted by believers in the paranormal or supernatural as the presence of a spirit or entity.

Choctaw Walking Along a Bayou Alfred Boisseau – 1847 (Wikipedia)

Choctaw tribe's ancestors go back 8000 years ago. They pass down their legends by oral tradition, the elders tell their legends to each new generation. They speak of Nalusa Chito, also known as a Impa Shilup known to eat souls, one must not think evil or this shadow spirit will creep into one's mind and eat their soul.

The Choctaw mention other shadow beings such as Hashok Okwa Hui'ga who leads astray people. According to the Choctaw it's heart is enclosed by shadow. Hashok Okwa Hui'ga  is similar to the Celtic will-o'-wisps, medieval Latin for fool's fire, a spooky light that looks similar to a lit lantern it appears over bogs, marshes swamps many lost travelers at night have been led to their death drowning in swamps due to following will-o'-wisps.

An 1882 oil painting of a will-o'-the-wisp by Arnold Böcklin. Wikipedia

The Choctaw people believe that every person has a shilombish means (outside shadow) who would tag behind them and a shilup means ghost or inside shadow. 

The shilombish,according to the Choctaw, were fated to wander the earth, it would scare people and it was a shape-shifter, it could transform into an owl or fox replicating their sounds. These Owl or fox sounds it made was a harbinger of doom to whomever heard it. 

Some folks encounters with Shadow beings concluded they are Extraterrestrials tracking the humans.

Shadow people have been discussed on talk radio shows such as Coast to Coast am back in 2006 with George Noorey interviewed Heidi Hollis an expert on this topic.

Source & Reference:

• Native Languages of the Americas: Choctaw Legends, Myths, and Stories http://www.native-languages.org/choctaw-legends.htm
• "Shadow Beings". Coast to Coast AM. 2006-03-27.
•  Heidi Hollis (October 1, 2001). The Secret War: The Heavens Speak of the Battle. iUniverse. ISBN 9780595203314.
• Featured image of Shadow man - Wikipedia, Public Domain