would it make sense that a broker would be buying

would it make sense that a broker would be buying and selling on the open market trying to get a profit but then buying and selling to the public at different prices to try and turn a profit? That would make sense to me, this way they report at the end of the day electronically then lag makes it seem like it was actually after hours. I could be way off but it kind of adds up in my "diluted" mind after a long day.