A nationwide manhunt is under way for a Chinese businessman suspected of involvement in the deaths of a family of four found murdered at their home.
Northamptonshire Police said they believed university lecturer Jifeng Ding, his wife Helen and their daughters, Alice and Xing, had been "tragically targeted" because of their business links to Anxiang Du.
Naming Mr Du, who lives in Coventry, as a suspect in the quadruple murder inquiry, detectives also revealed that the 52-year-old wrote a suicide note shortly before the murders are thought to have been committed.
Detective Superintendent Glynn Timmins told a news conference that Dr Ding, who worked at Manchester Metropolitan University, his wife, who was a part-time teacher, and their daughters, Alice and Xing, had all died from stab wounds.
The family members were found dead at their detached home in Wootton, Northampton, on Sunday, and police later established that a Vauxhall Corsa hired by one of the victims was missing from the address.
Warning the public not to approach Mr Du and confirming his status as a suspect, Mr Timmins told the news conference: "We want to seek the public's assistance in finding Mr Du so that we can question him about this incident.
"The public should ring 999 if they see the car or indeed Mr Du - my advice would be that neither Mr Du nor the car should be approached."
It emerged that Mr Du left a suicide note at his workplace before he was last seen on the day of the royal wedding, and was then reported missing to West Midlands Police.
Mr Du, who worked at a Chinese herbal medicine shop in Birmingham, was last seen on Friday morning, when the victims are known to have still been alive because Alice, 12, and Xing, 18, used their Facebook accounts.
Mr Du is described as being of slim build, routinely wears a baseball cap and is thought to have left his home in Coventry at about 10.30am on Friday.