Brussels Airlines Took My Carry On At the Gate Even Though I Followed Rules

I was flying with Brussels Airlines on September 5th, and I was careful to abide by their baggage policy. As required by the regulations, I only brought one carry-on bag and one personal item. Since I really didn't want my carry-on checked in, I stood near the front of the line at the gate to make sure it would accompany me into the cabin. However, the staff abruptly began removing some passengers' carry-on bags to be checked at the gate without providing a clear explanation. I was surprised by how haphazard the procedure seemed—some passengers boarded with both their personal belongings and carry-on, while mine was removed. I felt uncomfortable and singled out because I had complied with all the rules.