BONN — Days after an Israeli man hijacked a tourist bus in Cologne and killed two people, German police still are unable to provide the motive behind the bizarre seven-hour hostage drama.

Police officials expressed shock at the cold-blooded murders carried out by 31-year-old former Ramat Gan resident Leon Bor last Friday.

They described Bor, who is of Russian origin, as a "sadist" who enjoyed "killing for the sake of killing."

Bor, born Leonid Borshevsky, hijacked the bus 10 minutes after it left the tourist information center near Cologne Cathedral. Twenty-four tourists were on board.

Having immediately shot the driver, Bor used the tour guide as a human shield. He changed into a green uniform, ski mask and a fake dynamite belt that looked real enough to later convince police they were dealing with a professional terrorist.

An eyewitness summoned police. But when the first unit arrived at the scene, Bor opened fire, severely wounding one officer.

Speaking with police over a phone on the bus, Bor described himself as a member of the Russian mafia. He spoke with police negotiators in Russian as well as in broken German and English.

Late in the drama, Bor walked down the aisle of the bus asking the blindfolded and bound passengers to cite their nationalities.

When a 64-year-old woman said she was German, Bor shot and killed her, then took a Polaroid snapshot of her body. He then had a passenger photograph him in his combat uniform.

Shortly after Bor killed the German woman, a police commando unit stormed the bus. A sniper killed Bor with one shot.

Five hostages had managed to escape from the bus during the ordeal.

Police later found in Bor's bag a parachute and an electronic navigation instrument, which raised speculation that he may have intended to take over an airplane at a later stage of the hijacking drama.

Despite the circumstances surrounding the killing of the German woman, German police refused to say the murder was racially motivated.

Israeli police officials said they had little knowledge about Bor, who they said had no criminal record in Israel. In 1989, Bor immigrated to Israel from Russia, where he was born Leonid and in 1993 reportedly left Israel for the United States.

Israeli diplomatic officials in Cologne said Bor would be buried at a Jewish cemetery in Cologne unless a relative requested that his body be flown to Israel. But, they added, Bor apparently had no relatives living in Israel.