SPIONICA, Bosnia, June 9 -- Safeta Muhic is glued to her television set, feverishly flicking channels for another chance to see Serbian gunmen killing her brother.
''That's my brother falling down there,'' she says, catching the tail end of a short video clip played over some news headlines.
The grainy footage shows a thin teenager with hands tied behind his back stepping in front of a gunman dressed in black. He walks forward in silence, and then two bursts of automatic rifle fire hit his back and he flops to the ground.
Her brother, Safet Fejzic, went missing in July 1995, when he was 16 and in Srebrenica. He was thought to be among about 7,000 Muslim men and boys massacred by Bosnian Serb and Serbian forces at the tail end of the war in Bosnia.
But Ms. Muhic, a 23-year-old mother of two, did not know the full details of his death until this month, after the emergence of a videotape showing the killing of her brother and five other Muslim men. Initially stunned by what she saw, she now says she cannot help but try to see his last few moments again and again.
For more than a week now, the video, filmed by a member of the Serbian police unit that committed the killings, has been repeatedly shown on television in countries throughout the Balkan region. It was first shown in court on June 1, during the war crimes trial of former President Slobodan Milosevic of Serbia. In Bosnia, the tape has again brought the pain of that time to the surface for families like Ms. Muhic's. But it may be having an equally profound effect in Serbia, where the public has been reluctant to accept that their forces could have been involved in war crimes.
Since then, reporting about the video has dominated mainstream news media. Analysts say the cassette is the most significant piece of evidence to shape Serbian public opinion since the end of the Balkan wars of the 1990's. Usually only the country's more liberal news outlets carry reports about possible Serbian war crimes, but state-run television and all the national newspapers have carried pictures and articles about the killings.
One newspaper, Blic, published an article about the shock the videotape had caused among families of the police unit. The report said one girl had seen the tape on television and recognized her father among the killers. It quoted her mother as saying, ''Since then, she has not spoken a single word. She has just wept.''
''This tape has definitely had more exposure to the public than anything else I can remember,'' said Svetlana Logar, a polling expert for Strategic Marketing Research, based in Belgrade. Her company is conducting an opinion poll that will be released next week on reaction to the videotape.
While most foreign observers regard Serbia and Bosnia's Serb leadership as the main perpetrators of war crimes in that era, polls consistently show that most Serbs regard themselves as the main victims of the war. Those accused of war crimes are often presented as national heroes by the news media and the government.
After the tape's emergence, President Boris Tadic and Prime Minister Vojislav Kostunica of Serbia swiftly condemned the killings. Serbian authorities say five men shown on the videotape have been arrested, including the unit's commander, Slobodan Medic, known as Boca, and the police are searching for four more.
Throughout the 12-minute section of videotape that features the six prisoners, their captors joke and show no hesitation. The executions appear methodical. The four youngest prisoners are lined up, then walk forward to be shot, one by one. The two remaining prisoners, perhaps in their early 30's, are then ordered to drag the bodies to a nearby building, where they, too, are shot. Only one of them talks during the episode, to ask for some water. The cameraman takes care to film the bullets as they enter the bodies, including final shots to the head after they have fallen to the ground.
While watching the video, Ms. Muhic recognized her brother as he was ordered to get down from a military truck at the start of the section showing the prisoners. Why couldn't the cameraman have intervened to save someone? she asked, not knowing that he was also a unit member.
''I would like them to pay for what they have done,'' she said. ''I would like their families to feel the same pain that we have felt.''
Her brother's remains were recovered in 1999 and identified in 2003. But she still had no idea how he had been killed.
Ms. Logar says the message is coming at a critical time, because people were not talking about the war crimes and younger Serbians were not hearing about them.
''No one is talking here about the facts, whether or not you call them war crimes or not. People are forgetting, and few people are aware,'' she said in an interview. ''Instead, politicians talked about indicted persons and whether or not they should be transferred to the International Criminal Tribunal.''
Ljiljana Smajlovic, a political commentator and writer for the weekly magazine Nin in Belgrade, said the tape had brought a sincere sense of outrage in Serbia. She also said the tape may provide momentum for the arrest of one of The Hague's leading war crime suspects and the man suspected of orchestrating the Srebenica massacre, General Ratko Mladic, the commander of the Bosnian Serb army at the time.
Apart from the shock caused by the videotape, closer scrutiny of the unit behind the killings has also undercut the popular image many Serbians have held of their fighters, who have often been praised as valiant defenders of the homeland.
That view is born out in the killing tape and in another tape of the unit that is making the rounds on Serbian television. Both begin with a Serbian Orthodox priest blessing the forces and saying, ''The Turks are rising again. They come to take our sacred places,'' a reference to Serbia's former occupation by the Muslim-dominated Ottoman Empire. After the video emerged, the Orthodox Church condemned the killings.
The unit involved in the taped killings, called the Scorpions, was formed in 1991, at the start of Serbia's war with Croatia. Its official purpose was guarding Slavonian oil centers. But in operation, said the chief Serbian war crimes prosecutor, Vladimir Vukcevic, ''they were organized ad hoc to do dirty work.''
Over the next decade, the group fought in Bosnia between 1992 and 1995 and in Kosovo in 1999, by which time it had been incorporated into the Serbian police service.
In addition to the men now being sought in the videotaped incident, another former member is on trial in the killing of 14 people, including seven children in Podujevo, a town in Kosovo, in 1999.
While the tape has brought outrage, it has also brought defensiveness. In Sid, a town in northwestern Serbia that is the home of most of the men shown taking part in the killing, many people expressed ambivalence. ''Maybe the tape was doctored,'' said a betting shop worker, 29, who refused to give his name. ''You don't know what those Muslims had done, either. It was war. You can't put all the blame on one side.''
The tabloid Nacional echoed that sentiment, publishing a front-page picture on Thursday of what it said was a Serbian soldier being executed by a Muslim. The headline read, ''Here's a Serb.''