Police investigating the murder of a man shot dead at his Surrey home are to look at his business dealings in Spain.
Mr Blackett lived with his partner, 11-year-old son and baby daughter
Daniel Blackett, 36, was shot several times outside his home in Thorpe Green near Virginia Water in September.
The father-of-three regularly visited Spain and detectives think something in his background there or in the UK will help them find out why he was murdered.
An appeal for information was made on BBC Crimewatch on Thursday and a £25,000 reward has been offered.
Mr Blackett was killed just before 2020 BST on 18 September outside Blisland Lodge in Sandhills Lane.
He was living there with his partner, Nichola Jackson, one of his two sons, aged 11, and his baby daughter.
Police said they were making inquiries to establish details about the victim's businesses.
Det Chief Insp Ray Marley said: "We suspect that something in Mr Blackett's background is likely to give us an idea of why he was murdered.
"He was known to the police and had associates in Spain."
Mr Blackett's family was in the house at the time of the murder, along with his mother and grandmother.
They heard shots being fired outside before seeing Mr Blackett stagger into the house.
Det Ch Insp Marley said: "This was a particularly callous killing and that's why we're so keen to find out why this happened and who is responsible."
Mr Blackett's sister Sharon Clarke appealed for information on Crimewatch, which also included a reconstruction of events leading up to the murder.
She described her brother as a loving father whose "best times were with his children".
"Daniel would have been absolutely horrified to know that his son had witnessed his murder," she said.
The reward is being offered for information leading to the conviction of those responsible for the murder.