Video report by ITV News Corespondent Neil Connery
The mother of Harry Dunn has told ITV News that she promised her son on his deathbed she would fight for justice for him.
The parents of the 19-year-old who was killed in a "big fireball" following a road crash, have taken their fight for justice for their son to New York where they hope media pressure will persuade the US suspect in the case to return to the UK.
Anne Sacoolas - the American motorist suspected of colliding with Mr Dunn - fled back to America shortly after the incident. A wife of an intelligence officer, she is said to be covered by diplomatic immunity, though that protection is now in dispute.
Speaking to ITV News, Charlotte Charles said at the time of Harry's death the family thought justice would be "simple".
Ms Charles said: "I promised him at the hospital, after we'd lost him, I promised him we would do all we could do get justice for him. But we thought it was going to be really simple then. We didn't know she was going to flee. We just thought it was a clear cut case."
Harry's father Tim, told ITV News he had gone to the scene of the collision and was by his son's side during his final moments. His presence, he said, gave some comfort to his dying son.
"He was on the stretcher, they were just pulling him out of the ditch.
"So I managed to speak to him and say, 'Harry it's your dad, be calm and let them do what they need to do.'
"It helped to speak to him. He knew I was there, which I think helped him to know that he had someone in his corner. That his dad was there for him."
The family had pleaded with the US suspect to return to the UK and do the "humane thing."
Earlier on Monday, Harry's parents spoke on American breakfast TV about their campaign to get justice for their son, who died when his motorbike crashed with a car outside RAF Croughton in Northamptonshire on August 27.
The teenager's parents told a press conference in New York they felt let down by the decision to allow Ms Sacoolas to flee the country and return to America.
The family said CCTV evidence in the moments leading up to the crash made it "a clear-cut case".
A tearful Ms Charles told reporters: "We just want to know that she is being brought back to the UK.
"You know, that would be a huge step in the right direction.
"It's the only right thing to do.
"It's the only humane thing to do."
They said their "grief is on hold" until Ms Sacoolas travels back to the UK and faces questioning by Northamptonshire Police.
Ms Charles added: "All of our grief has gone on hold, it's coming out in other horrific ways, your legs feel like lead, you're in pain morning until night that no painkillers can take away.
"You're not able to cry, because we can't understand this whole situation as to why she [Anne Sacoolas] would have left us without wanting to meet us back then."
Ms Charles said the family do not wish "ill-harm" on Ms Sacoolas and that she had written to the family expressing her “deepest sympathies and apologies”, but added that she needed to hear the apology from her "in her own words."
"Just hearing it through a statement, we're seven weeks in now, it's a bit too much too little too late, I'm afraid," Ms Charles said.
While Mr Dunn added: "There's just no way I can start grieving yet, as a family we can't start, we need this resolved.
"Somewhere, somebody has made a decision to give this lady immunity.
"On that night there was an accident, a lady made a mistake, she killed our son, she didn't mean to kill him, she didn't mean to have an accident, but you cannot walk away from that and just leave and expect nothing to happen.
"Our boy died and he deserves to have some justice.
"That's all we want."
The Foreign and Commonwealth Office (FCO) has written to the family informing them Ms Sacoolas did not have diplomatic immunity.
The CPS is now involved in the investigation and Northamptonshire Police is seeking advice from them about what their options are.
Police are also liaising with the FCO and the International Crime Co-Ordination Centre, but the suspected driver needs to be in the UK to be interviewed, arrested or charged.