Updated

Police in Illinois say they are investigating an incident during which an off-duty officer threatened a black teenager and pinned him to the ground for trespassing.

A highly viewed Facebook video shows a man later identified by Lansing police as an off-duty officer detaining the black youth Saturday after the 15-year-old and a white minor refused the man's orders to stay on his property.

Police said the white youth showed signs of being involved earlier in a fight that was reported to authorities and was confronted by the man when the youth sat on the man's porch. The white minor was leaving with the black teen when the confrontation began.

The video, made by the white youth, shows the man pinning the black teen to the ground with his knee, his hand on the boy's neck.

The boy is heard telling the man to let him go. The man is heard pointing out the boy is on his property and he could kill him. He also is heard telling the 15-year-old to summon the white boy back onto his property.

In a statement released late Tuesday, the Lansing Police Department said the off-duty officer "became involved when he was approached by two other subjects involved in the fight." It went on to say the black youth was "temporarily detained for further investigation until the arrival of on on-duty officers." The officers took custody of the youth and took them to their homes.

A dispatcher said Thursday a detective involved in investigating the case was unavailable for comment.

A lawyer representing the black teen and his family said the Lansing police statement was inconsistent with the video and eyewitness reports.

"The video speaks for itself," said Andrew M. Stroth. "(The Lansing Police Department) is conflating two separate and distinct incidents. And what I want to know is how was that officer possibly justified to use excessive force and threaten to kill a 15-year-old boy?"

Stroth said the family is "demanding" a full investigation from Lansing police in order to determine whether or not they will pursue any litigation.