9. A 5 year old child had an upper respiratory infection 5 days ago. Today, his mother brings him to the emergency room because his urine was bright red this morning. Upon admission, he appears pale, his hemoglobin is 6.4 g/dL, his urine and serum have free hemoglobin, and his direct antiglobulin test (DAT) is weakly positive with anti-C3 only (anti-IgG is negative). Which of the following is most likely TRUE?