New kitten, have question

Hello, I am new to the forum and have a question about our new kitten. He is about 12 weeks and we got him from a shelter on Saturday. All of Saturday he was fine, full of energy, eating well, paying. Sunday morning he had pooped on the bed and it was diarrhea with bright red blood. I separated him from my other cat, who is about a year old and kept my eye on him. He has only had that one incident, not another one like that and it has been over 24 hours (and he is still acting fine). I'm stumped on what could have caused it. Do you think he's ok now and it was just a change of environment or stress? Thanks!

Did he get a clean bill of health from the shelter before you adopted him?  If not, he needs to be seen by your Vet before integrating him with the rest of your household. 

As the the bloody diarrhea, how much bright red blood was there?  If just a little bit, I would say it's probably ok, as long as he doesn't have more.  But more diarrhea in a kitten can be very bad, as it can dehydrate them quickly, and that's an issue, as they can go downhill quickly. 

I would think diarrhea could definitely be stress related due to change in environment.  Hopefully he's fine now   Are you feeding him the same thing they fed him at the Shelter?  You  might not want to change his food too quickly, as that can cause digestive distress.

I had the same problem with one of our kittens a few months ago. The vet wormed them all and gave the one with bloody diarrhoea some prokolin. Problem solved. Good luck x

I would get him to the vet for a check up and to meet the vet.  Could be parasites, even if treated previously.  It's not uncommon to need a repeat deworming due to the life cycle of the parasite.