While Sacoolas was named in British media reports and by the United Kingdom prime minister as the suspect driving the vehicle that allegedly involved in the collision with Dunn's motorcycle, the US State Department declined to confirm her or her husband's identity.
Johnson told the BBC that he would raise the issue with the White House if the situation is not resolved soon, insisting that he hoped "Anne Sacoolas will come back and... engage properly with the processes of laws" in the UK. On Sunday, they confirmed "the auto was being driven on the wrong side of the road".
"All we need to do is meet her", Ms Charles told the broadcaster.
Speaking to Sky News on Sunday, Housing Secretary Robert Jenrick said Mr Dunn's family "have our absolute assurance that we're going to do everything we can to resolve this".
British Foreign Secretary Dominic Raab said he called the U.S. Ambassador to express the U.K.'s disappointment.
"Northamptonshire Police followed all of its usual procedures following the incident, including liaising closely with the suspect, who engaged fully with us at the time and had previously confirmed to us that she had no plans to leave the country in the near future", Johnson said in the statement.
Their departure reportedly was urged by lawyers and US Embassy officials.
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But not everyone thought Bieber was throwing shade, with one person tweeting: "I legit don't think they're trying to make this a big deal, they just saw it and were laughing about it:/ but everyones freaking out".
Mrs Charles said Ms Sacoolas had "left a family in complete ruin", adding: "We're broken".
Tragic: Harry Dunn, 19, died after a head-on collision outside an airbase.
"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", it said. "We later lost him in hospital", she said.
The 42-year-old mother of three has returned to the U.S. where she is hiding behind diplomatic immunity. I would say, come back face justice, let's see what happens.
Anne Sacoolas, 42, a mother-of-three, claimed diplomatic immunity to avoid prosecution despite not being on the official London diplomatic list.
The fatal crash has left Mr Dunn's family heartbroken and demanding justice. "Please help us. We won't be able to grieve and move on and try put the pieces of our shattered lives together until we get justice for Harry". This means that they can avoid arrest for nearly any crime in another country, although the home country is allowed to waive immunity, WaPo reported.
The teenager's father Tim Dunn said: "It's appalling".