It involves an incident over the weekend and it was all caught on video.
The Tulia police chief, Jeffrey Yarbrough, confirms they are investigating the incident in which a man is thrown to the ground by the sheriff while handcuffed.
But, the incident before the camera was rolling is also under investigation.
It all started Saturday morning. Lawrence Draine, 23, says he was looking for junk cars to buy when a man with a gun started following him.
At one point, Draine stopped his vehicle and asked the man driving a pick-up why he was following him. The driver allegedly pulled a shotgun on Draine and that's when the sheriff arrived.
On the video, you can hear Draine's girlfriend, Tiffany Smith, trying to explain to sheriff Wells what happened.
"He been following us. He pulled a shotgun. We trying to tell you what's going on but you don't want to listen." Smith said on the tape.
Wells is then seen throwing the handcuffed suspect to the ground after he stands up.
When Smith began recording the incident, she was allegedly threatened with arrest also.
Chief Yarbrough says he has confirmed many of the events in the video.
"We've been able to confirm through our investigation that when the sheriff arrived, the two individuals, Mr. Draine and Mrs Smith approached the sheriff, tried to explain that the individual in the truck had a shotgun. Supposedly the sheriff told the guy in the truck to leave. "
Chief Yarbrough wants to know why the sheriff allowed the man with the gun to leave but, detained Draine for failure to identify himself.
Yarbrough says if the man in the pickup did pull a gun on Draine, then he should've been arrested for deadly conduct.
The police chief says two different witnesses confirm Draine's account but the man in the pickup denies he pointed a gun at Draine.
Once the police department is done with its investigation, both cases will be turned over to the county attorney.
Copyright 2015 Nexstar Broadcasting, Inc. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.