A 1 year-old male patient was brought in with passing blood in the stools. Thought of bacillary dysentery and was put on cefixime. A day later he passed frank blood per annum. USG done to rule out intususception. It showed mucosal edema of colon.

No e/o intususception. 48hrs latter he developed ecchymosis and petechial spots. What can be the diagnosis? What should be further management?