It does not look like mating. He or she is just often chasing them, pecking them, yelling when they are where he cannot get etc.
If this is a cockerel, when would he attempt to be dominant in the flock? We will be out and not able to monitor the flock closely for several weeks. Just petsitter changing water etc. I am a bit concerned that he may start to attack our adult hen. We cannot have a rooster anyway so now would be the time to get him out. But if it was a hen I would not be ready to let her go so quickly.