Tipu Sultan, 32, a father-of-two, was shot at close range outside Herbs n Spice Kitchen, Lake Avenue, South Shields, on 7 April.
Northumbria Police confirmed it had arrested two men aged 47 and 24, and a woman, 27, on suspicion of murder.
A 44-year-old woman has been arrested on suspicion of assisting an offender.
A reconstruction of the killing was broadcast on the BBC's Crimewatch programme, which police said resulted in a number of fresh leads.

It comes after two cabinet ministers stepped down on Tuesday over separate scandals, which means a political reshuffle is likely in 2016.
Liberal senator Eric Abetz called for Mr Abbott to make a comeback saying he has "more to offer public life".
Abbott was unseated by current Prime Minister Malcolm Turnbull in September.
"I'm on the record as saying that I believe Tony Abbott has more to offer public life in Australia," Mr Abetz told the Australian Broadcasting Corp (ABC).
"I hope that he stays in the Parliament and I hope that there will be a place for him, a prominent place for him, in any future ministry should he decide to stay.
Another politician calling for Mr Abbott's return was Nationals Senator John Williams, who told the ABC the move would help "heal the wounds of the past".
Cities minister Jamie Briggs resigned yesterday after a female public servant lodged an official complaint about his behaviour in a Hong Kong bar in September.
Mr Briggs said that he had failed to live up to the high standards expected of a government minister.
Special Minister for State Mal Brough also stepped aside pending the result of a federal police investigation into alleged his role in the illegal procurement of a rival politician's private diary.
Deputy Prime Minister Warren Truss, who leads the Nationals, is widely predicted to retire from politics before the next federal election.
An announcement on Mr Truss's future would provide the catalyst for Mr Turnbull to reshuffle his frontbench.
Four people have been arrested in connection with the murder of a man who was shot dead outside a takeaway.
[NEXT_CONCEPT]
Supporters of former Australian Prime Minister Tony Abbott have made calls for him to return to a senior government position.