Good Morning and welcome! I am Dr. Loretta, a licensed veterinarian and I am happy to answer your question.
Oh my! Poor Murray! He has been frightened by something that has caused severe stress causing this digestive disturbance. This is treated by following these instructions:
Fast Murray for 12-24 hrs to allow the digestive tract to calm down and heal.
Give Murray Pepcid AC or Famotidine at 0.5 mg per pound every 8 hrs. That can be purchased over the counter at the pharmacy.
Give only small amounts of water during the fast or ice cubes
After the fast, feed rice and boiled chicken (2/1)
Wean Murray back to his regular diet. This blood you see is due to this digestive issue and will resolve once this issue resolves. I would also recommend purchasing Feliway at the pet store. This is a feline pheromone that acts as a calming agent and will help poor frightened Murray past this. Your other cat sees Murray as a foriegn cat because of this stress. This will pass.
Does that make sense to you?
Please let me know if you have ANY other questions. My goal is to give you 100% satisfaction and if you are not yet satisfied, please REPLY so I can clarify for you.
Sincerely, XXXXX XXXXX