KIEV, Ukraine—Ukrainian police are investigating the grisly murder of a judge and three family members whose decapitated bodies were discovered over the weekend in the judge's apartment, officials said Monday.

The beheaded bodies of Judge Volodymyr Trofimov, 58, his wife, son and the son's girlfriend were discovered by the judge's stepson, who came to visit the family Saturday in their apartment in the eastern city of Kharkiv, federal officials said.

The heads are still missing, Interior Minister Vitaly Zakharchenko said.

Investigators believe the slayings could either be related to Trofimov's work or to his renowned antique collection, Interior Ministry spokesman Serhiy Burlakov said.

There were no obvious signs of a break-in and police believe that two perpetrators had carefully prepared for the crime, Zakharchenko said. Authorities have promised a 200,000 hryvna ($24,000) reward for those with information that would help track down the killers.

Trofimov has ruled in several thousand cases during this 30-year career as a judge and the slayings took place on a national Ukrainian holiday for judges.

Ukrainians are widely dissatisfied with their country's Soviet-style justice system, in which more than 90 percent of the cases end with guilty verdicts. Among the Council of Europe's 47 member states, Ukrainians make up the fourth largest number of complaints filed to the European Court of Human Rights.

The perpetrators could also have been looking for Trofimov's internationally-known coin collection, or his collections of ceramic figurines, medals and antique furniture.

Some of the judge's belongings were missing from his apartment, according to investigators, who would not provide further details.

Trofimov's murder was reminiscent of the 2000 killing of investigative journalist Heorhiy Gongadze, whose beheaded body was found in a forest outside Kiev. Gongadze's head was discovered some 10 years later based on the testimony of a suspect who is currently on trial for his murder. Three former police officers have been convicted of carrying out the killing, but the masterminds of the crime have not been brought to justice.

Trofimov is survived by his father, a 90-year-old former judge, and his 86-year-old mother, the Interfax news agency reported.