An air traffic controller who ordered a passenger plane into the path of another aircraft over Germany — a crash that killed dozens of Russian children — was stabbed to death Wednesday in front of his wife.

The attacker was a heavily built man aged 50-55, possibly Eastern European, with graying hair and a three-day stubble. He showed up at the controller's home Tuesday night, spoke briefly to the controller in broken German, killed him, and fled on foot.

Beyond that description, police said they have no leads on the killer but are investigating a possible link between the stabbing and the crash 19 months ago that killed 71 people. The accident was blamed on the controller, a 36-year-old Danish citizen who has never been named by authorities.

"There wasn't much said," District Attorney Pascal Gossner told The Associated Press. He declined to say what words were exchanged between the killer and victim, because it is part of the investigation.

He also said there were other people there at the time of the murder, but would not say if they included the couple's three children. The controller died at the scene, police said.

"We are looking at all sorts of aspects," said Gossner of possible motives — including that the murder was connected to the July 1, 2002, crash over southern Germany, an area run by Swiss air traffic.

At the time, the controller was on duty alone in the Zurich control room, because a colleague was taking a break. He gave only 44 seconds' warning to the Bashkirian Airlines (search) plane and a DHL cargo plane that they were getting too close.

The controller told the Russian plane to descend, countering the jetliner's onboard collision-avoidance system which was demanding it climb, according to preliminary accident reports.

The pilot followed the instructions of the controller — sending the jetliner straight into the DHL cargo plane, which also was descending in accordance with its collision-avoidance equipment.

Those killed in the crash included 45 prize-winning Russian schoolchildren, bound for a vacation in Spain.

German authorities have yet to release their full report on the accident but said they would not be hampered by the controller's death as he had already been interviewed extensively. The Dane was placed on medical leave after the crash. He was later allowed to return to work but given other duties.

In an interview with a German magazine two weeks after the accident, he expressed his sorrow for the crash. "As an air traffic controller, it is my task and duty to prevent such accidents," he told Focus.

Skyguide (search), the Swiss company the controller worked for, said it was appalled by his murder and that its employees "were in shock."

The company received no threats after the collision, Skyguide chief Alain Rossier told a news conference, and investigators were trying to establish whether the controller received any threats personally.

At the time, Swiss President Kaspar Villiger (search) canceled plans to attend a funeral for the children killed in the crash, because officials in the Russian city of Ufa said they could not guarantee his safety.

In response to the stabbing, Skyguide reduced by 40 percent the number of planes it allowed into the airspace it controls to give other controllers time to come to terms with the killing. Of 28 employees scheduled Wednesday, seven were too upset to work, a spokesman said.

The employees and the controller's family are receiving counseling, and Zurich state police have helped organize protection, the company said.