Slavi Binev was shot dead at his home on Reznyovete street in Sofia, next to Alexander Pushkin boulevard and close to the Boyana Residence. Early reports put the shooting in the Pavlovo district.

Accounts of the car also differ. The interior ministry first said the group came in a Lexus, but security camera footage shows a silver Range Rover.

Earlier on this story: Slavi Binev killing in Pavlovo: main line of inquiry is an unsettled money dispute

Investigators' main theory is a row over unsettled money. They say there is not yet enough evidence of a contract killing, and they think the dispute may have flared up on the spot.

One of the men in custody has known Binev for years, and the two are linked through taekwondo. Within hours of the killing, it emerged that Binev, the detained man and his wife have shared business and personal ties.

The detained man's wife is an architect. Her father, Stoyan Yanev, is a former chief architect of Sofia. She and Binev are partners in the construction firm Evinko Ltd. Polanta, a gemstone and precious metals firm, is also owned by her and her husband.

Unofficial and unconfirmed information says Binev and the woman had a romantic relationship, so a personal motive is also seen as possible. There is no information that she has been charged. Police have not said they are checking a personal motive.