A second man has been detained in Plovdiv over the killing of businessman Iliyan Filipov. Unofficial information from sources familiar with the case says he is 42, from Pazardzhik, and is being held for up to 72 hours.

Filipov, 53, was shot dead in the early hours of 30 September, in front of the lift in an apartment block in the Hristo Smirnenski district.

Earlier on this story: Gun used to shoot businessman Iliyan Filipov dead is found

On Friday, the interior ministry and prosecutors confirmed that the gun was found outside Plovdiv and has been added to the case file as evidence. In early October, interior minister Ivan Demerdzhiev had said the weapon had not been found.

The first man detained is Slavcho Megerov, 51, a former employee of Filipov. Police arrested him in Sofia hours after the killing, and on 1 October prosecutors charged him with premeditated murder. Prosecutors say the motive was an unsettled financial dispute between the two men.

Megerov appealed against his detention, but the Court of Appeal kept him in custody, the toughest pre-trial measure. The judges said he could go into hiding or commit another crime.

The suspect was tracked through security camera footage from the area. It shows the car in which, according to investigators, he arrived, and his route to the building.

Shortly after 1am, the footage shows a car parked in front of the entrance. Filipov gets out and walks towards the building. He went there because a female relative had called him about a suspicious masked man in the entrance hall.

"For about 15 minutes the attacker waited at the side of the building," the court's reasoning says. The cameras also filmed a woman who witnessed events going into the building, and the man's movements.

"At the same minute, the man who had been waiting at the side of the building also headed for the entrance and went in," the court heard. Minutes after Filipov went in, the same man was filmed running out of the building.

Witnesses say Filipov gave Megerov money to place bets on sporting events, and when a bet won, Megerov was supposed to pay him the winnings. They mention sums from €7,669 (15,000 leva) to €10,226 (20,000 leva), and say the businessman handed over much larger amounts for bets.

So-called "black toto" betting is a crime against sport under the Criminal Code. It is punished with a fine or prison, depending on the nature and seriousness of the offence.