The bad guys were really expecting this to be a quick job with no casualties and no trouble, so they didn't bring any restraints with them, so they had to improvise. They really needed to keep this MP secured and quiet as long as they could, so they would have all the time in the world to escape.
The MP was quickly secured with the MP's own handcuffs to the bollard, but then one of the guys thought that's not good enough, he would get free in no time, so then he started undoing the MP's belt and pants then just pulled them down, the MP started complaining, but he was immediately gagged with tape. The guy pulled the pants and belt over the other bollard, completely stretching the MP between the two bollards, there's no way he could get free from this until his relief comes for the next shift.