The family of 23-year-old student Gabriel Ferez has made an appeal for witnesses on behalf of their son, who was murdered in London.
Gabriel's parents, Francoise and Olivier Ferez, said: "To those who committed this crime against our son and his friend we say: it is possible you did not anticipate how this might turn out. We plead with you to turn yourselves in to the police.
"You will not be able to live in hiding forever. You may be scared and feel like a coward, but you must recognise this terrible mistake you made. Rest assured that we will not leave you in peace.
"To the people of London we say: we respect the UK and its reputation for fairness.
"We ask everyone to be vigilant against crime; but especially those who live in the area of London where our son died.
"If you know of anything unusual or suspicious that may help in this investigation - someone acting strangely, something you overheard, someone who has gone missing - please do report this to police."
Gabriel Ferez and Laurent Bonomo were stabbed hundreds of times then left in their burning flat. They were exchange students studying at London's Imperial College.
Francoise and Olivier Ferez urged any witnesses to come forward and not to feel "useless or like an 'informer'", calling their son an "angel".
Police arrested a 21-year-old man during the early hours of Saturday on a street in south-east London in connection with the murders.
Scotland Yard detectives are also asking for information on an earlier break-in at the property during which a laptop was stolen.