I've had a two week old chick kill its sibling one morning by pecking it on the head. Then it immediately started on another chick. I isolated it for a day and it stopped that behavior. I had a 15 week old cockerel decide to kill a sibling cockerel one morning. It did by pecking the head, but never bothered any other siblings. These were not overcrowded.
I don't think that is what is going on with yours. I think that chick was pecked and it started bleeding. It could have been a new blood-filled feather growing in that got pecked. Once they see blood they can turn cannibalistic. I agree, this type of behavior is more typical when they are overcrowded but not all cases are due to overcrowding. Sometimes it just happens.
I have successfully housed over 20 chicks in a 3x5 feet brooder until they were 5 weeks old without problems but they were getting really crowded. That could be a contributing factor.
I'd isolate that chick until it heals, at least no longer bloody. If at all possible, house it across wire from the others as that can ease reintegration. Sometimes a flock decides to run off or kill another flock member for no known cause so I'd be cautious putting it back in with them, but I think it was probably a blood
You don't say how many chicks in that space, but to me that is a rather limited area for 3+ week old chicks. I would monitor closely in case they start pecking on another chick.
i have 6 chicks
You don't say how many chicks in that space, but to me that is a rather limited area for 3+ week old chicks. I would monitor closely in case they start pecking on another c