On the morning of July 4, an American marketing professor was walking towards his ex-wife’s house in Athens to pick up their two young children. It should have been an unremarkable, if strained visit – the couple had apparently been disputing the terms of custody arrangements.

Greek police have arrested five people over the killing of a University of California at Berkeley professor who was shot dead in an Athens suburb earlier in July, police said.

Greek officials say the broad-daylight attack came one day after a custody hearing over the victim's 10-year-old twins.