The force had previously urged the public to not share footage of the build-up to the stabbing or the previous incident, in nearby Whitworth Park, on social media.
Mohanad was stabbed near the corner of Monton Street and Moss Lane East.
Ch Supt David Meeney said the referral to the IOPC was “mandatory”.
“Our investigators have been working around the clock and during this investigation we have undertaken several warrants in relation to this incident as part of our commitment to getting justice for Mohanad and his family,” he said.
Mohanad’s family said earlier: “His life has been cut tragically short, it is difficult to comprehend that seeing your son head off for school in the morning would be the last time that we would see that handsome face.”
They said the 15-year-old, who had an older sister and brother, had “an uncanny ability to make you laugh, making it sometimes difficult to be serious with him”.
“Mohanad had many friends, he was loyal and often played the class clown, simply to see them laugh,” his family added.