You may had an experience with what some people would call a "shadow person" here is a definition from wikipedia:
Shadow people (also known as shadow men, shadow folk, or shadow beings) are said to be shadow like creatures of supernatural origin that appear as dark forms in the peripheries of people's vision and disintegrate, or move between walls, when noticed.[1]
Reports of shadow people are similar to ghost sightings, but differ in that shadow people are not reported as having human features, wearing modern/period clothing, or attempting to communicate. Witnesses also do not report the same feelings of being in the presence of something that 'was once human'. Some individuals have described being menaced, chased, or in some rare instance, attacked by shadow people. There have also been reports of shadow people appearing in front of witnesses, of which they stay there or lingering for several seconds before disappearing. Witnesses report that encounters are typically accompanied by a feeling of dread
Reports of shadow people have existed throughout history. The observer generally reports seeing a dark shadow that resembles the form of a human which appears and moves of its own accord. The figures does not have distinguishable facial features and may be either much smaller or larger than a human. They are often noticed as movement from the corner of the eye, sometimes disappearing when the observer turns to investigate.
Shadow people may move quickly across a room, usually disappearing through the wall or closed door. Many report a feeling of extreme dread or fear accompanying the sighting. Others have reported that when the shadow moves across their physical being a feeling of extreme cold overcomes their body. This sensation of coldness disappears once the apparition is gone.
Many believe that shadow people are the ghost of someone who has passed on but is not able to leave this physical world for some reason. Others believe that shadow people are creatures of another dimension that somehow overlaps our own, causing it to be partially visible. Many have captured images of what they believe to be shadow people in photographs.
Other paranormal enthusiast believe that shadow people were never human at all and are a demonic spirit that embodies pure evil. Some have reported seeing glowing red eyes, but generally shadow people appear as a simple form that resembles the human form. Some report the presence of a hat or cape. One thing in common is that shadow people often try to avoid detection and like to observe from corners of the room, usually at night.
Here is another article: http://www.associatedcontent.com/article/362588/hauntings_what_are_shadow_people.html
Shadow people have been observed in daylight and many have observed them in full vision, although it is common to catch a sighting from the corner of the eye.