Fortunately, the police did have clues. They "established that two Sony PSPs are missing and believe they were taken during the incident on Sunday when the two men were killed." They also released one of the PSP's serial numbers, SO1-0613169-C. Today, a 21-year old man has been arrested in connection with the murders. It is unclear whether the serial number released helped solve the crimes, but it is good to hear a culprit has been apprehended in these grisly murders.
[Note: Due to the tabloid nature of the Sun, here is the BBC's take.]