The parents of a teenager who was killed in a head-on collision say they are "utterly broken" after the suspect, a US citizen, claimed diplomatic immunity and left the country.
Harry Dunn, 19, was killed in an accident near RAF Croughton in Northamptonshire on 27 August. It is an American spy base.
Police told Sky News that their initial findings show that Harry was riding his motorbike on the correct side of the road, but that a woman, who pulled out of the airbase onto the wrong side of the carriageway, hit him head-on. He suffered multiple injuries and died later in hospital.
Sky News can reveal that the suspect is the wife of a US diplomat who claimed diplomatic immunity following the incident.
Dependants of diplomats can be covered by immunity.
Speaking exclusively to Sky News, Harry's mother Charlotte Charles said: "Everyone loved him, we're utterly broken inside and out, everything hurts day and night, it's an effort to do anything, I ache from it, every limb, every internal organ hurts."
Andrea Leadsom, the business secretary and South Northamptonshire MP, tweeted in response to Mrs Charles' comments to Sky: "I met Harry's family yesterday. They are totally heartbroken. We have to get proper justice for Harry and closure for his family."
Meanwhile, Labour's education spokesman Angela Rayner, said on Twitter: "This is heartbreaking and nobody can be above the law. If you are here in the U.K. then you must abide by our rules. This family deserve answers and respect shown to their son."
Superintendent Sarah Johnson from Northamptonshire Police said: "We had met with the suspect in the presence of legal advisers in order to identify the best way forward.
"During the course of that meeting we were aware that diplomatic immunity had been raised as an issue, we then made immediate application for a waiver in order for us to undertake further investigations and interview.
"Unfortunately, we were latterly advised that the waiver had been declined and the suspect had left the UK."
The US embassy has confirmed to Sky News that the woman has left the UK. We understand that someone on the American side told the family to go back to the US.
In a statement, Foreign Secretary Dominic Raab told Sky News: "I wish to offer my condolences to the family affected by this tragic incident.
"I have called the US ambassador to express the UK's disappointment with their decision, and to urge the Embassy to re-consider it."
The decision has left Harry's family even more bereft.
"We don't know how we can start to grieve for him," Ms Charles said. "We have nothing. No justice. We have nothing to put our minds at rest that she's even remorseful."
Harry's father, Tim Dunn, said: "We're disgusted, appalled, how she could be having this cloak wrapped around her. I'm angry that someone could do this and then get on a plane and go.
"I can't believe she's living with herself."
Harry's family received a letter from the US ambassador to the UK, Woody Johnson, expressing "profound sadness".
In a statement, the US Embassy in London told Sky News: "We express our deepest sympathies and offer condolences to the family of the deceased in the tragic August 27 traffic accident involving a vehicle driven by the spouse of a US diplomat assigned to the United Kingdom.
"Embassy officials are in close contact with the appropriate British officials on this matter. Due to security and privacy considerations, we cannot confirm the identity of the individuals involved, but we can confirm the family has left the UK".
In a later statement, they added: "Any questions regarding a waiver of the immunity with regard to our diplomats and their family members overseas in a case like this receive intense attention at senior levels and are considered carefully given the global impact such decisions carry; immunity is rarely waived."
Sky News has tried to contact the woman but she hasn't responded.
"No one can settle," said Mr Dunn, adding: "We can't quite understand this is actually happening, or has been allowed to happen".