A pre-inquest hearing into the death of a student who was stabbed to death has been adjourned after a possible new witness contacted the family.
Yousef Makki, 17, was stabbed in the heart with a flick knife in Hale Barns, Greater Manchester, in March.
Security guard Paul Hughes reviewed CCTV, and believed there was a delay in calling for an ambulance, Stockport Coroner's Court heard.
Yousef's family said they have "a lot of unanswered questions".
The family and their lawyers asked senior coroner Alison Mutch for more time to gather further information and also take a statement from Mr Hughes.
Ciara Bartlam, representing the Makki family, said they are "well aware" an inquest was not about "blame".
But she said that at a family vigil this week at Manchester Cathedral, Yousef's sister Jade Akoum was approached by Mr Hughes, who worked as a personal security guard for David Beckham and runs a private security firm employed local residents to patrol the streets.
Ms Bartlam said Mr Hughes had viewed CCTV footage and had "particular concern" that Yousef "walked around a quarter of a mile" before he collapsed and an ambulance was called.
"An issue for the family is whether an ambulance was or should have been called earlier," she said.
The inquest has now been adjourned until 20 December.
Outside court, Ms Akoum said: "We have a lot of unanswered questions.
"This could help us answer those questions that we did not get answered during the criminal trial."
Joshua Molnar was cleared of the murder and manslaughter of Yousef, but was detained after he admitted possessing a knife.
A second defendant, a 17-year-old known in court as Boy B, who also admitted possessing a knife was detained for four months.
The trial heard Molnar acted in self-defence when Yousef pulled out a knife in a row over an attempt to rob a drug dealer.
Ms Mutch told the hearing, in light of the trial conclusion, she had to make a decision on whether a full inquest needed to go ahead or not.
She said if an inquest is to take place, it cannot come to a conclusion "inconsistent with the findings of a criminal court".