Stephen suffered critical injuries following the incident in Thurnscoe on Friday, 5 June and sadly died two days later. His family is being supported by specialist officers.
Five people are in police custody after being arrested on suspicion of murder.
A 36-year-old man, a 34-year-old man and two 15-year-old boys who were arrested on Saturday on suspicion of assault and bailed have now been re-arrested on suspicion of murder. A 34-year-old man is also under arrest on suspicion of murder.
Another 35-year-old man has been bailed after he was arrested on suspicion of murder on Sunday.
Police are now appealing for information about two incidents in Thurnscoe last week as they try to build up a picture of the circumstances leading up to Stephen’s death.
Detective chief inspector Mark Oughton, senior investigating officer, said: “My appeal for information today is three-fold. It begins with an incident that took place in Derry Grove Park just before 8.30pm on Thursday 4 June, when police received a report that Stephen – who was also known locally as Squeek - was unconscious in the park. He was checked by paramedics and returned home a short time later.
“Were you in the area at the time? Did you hear any kind of disturbance? Were you driving a car with a dash-cam that may have footage that would help our investigation?”
Detective chief inspector Oughton added: “The second part of my appeal is for information about the suspected serious assault that took place the following day, Friday, in the Houghton Road area of Thurnscoe, at around 7pm. Police received a call from ambulance staff reporting concerns for Stephen, who had been taken to hospital with a serious head injury.
“Were you on Houghton Road or in the surrounding area between 6.30pm and 7pm? Did you hear or see anything that was unusual?”
Police also want to hear from anyone who may have seen Stephen in the Thurnscoe area at any time on either Thursday 4 or Friday 5 June.
Anyone with information should call 101 quoting incident number 650 of 5 June 2020.