Chicago police have opened a homicide investigation after the Cook County Medical Examiner determined that nine-year-old Elijah Flores died of blunt-force head injuries sustained during an altercation at the Clinton Green Line station on Aug. 10. According to police, a 22-year-old man accompanying the boy became embroiled in a dispute with two other men on the station platform. One assailant struck the man in the back with an object as he tried to carry Flores down the stairs, causing both of them to tumble. Flores suffered a skull fracture and was taken to Lurie Children’s Hospital, where he was pronounced brain-dead and died on Aug. 17. Investigators are reviewing station surveillance footage and searching for the two unidentified suspects, who fled after the assault. No arrests have been made. Flores’s family said the fourth-grader’s organs were donated to other patients. Community advocates have joined relatives in urging anyone with information to come forward, while the Chicago Transit Authority offered condolences and pledged to assist the inquiry.