Their demand: the withdrawal of Russian forces from neighboring Chechnya.
Two days later, amid explosions, shooting and scenes of chaos, Russian forces moved to end the hostage drama. But Beslan became a byword for tragedy. More than 300 of the hostages -- half of them children -- were killed in the botched rescue attempt. According to the authorities, 31 of the 32 hostage takers also died.
Only Nurpachi Kuliev survived. He was found hiding under a truck outside the burning school building. Russian special forces rescued him from a near-certain mob lynching.
The hatred of an entire community is now focused on this one man. This puts huge pressure on the North Ossetian court. Yesterday's proceedings, in fact, had to be adjourned until tomorrow following an emotional outburst before the judge by some victims' relatives.
Many of them say they see no need for an official trial, as Elizaveta Kargieva told RFE/RL outside the courthouse yesterday.
"We're going to watch him, to see how he looks us in the face," she said. "There's no need to try him. They've already found out everything from him. He should be cut up, cut into pieces, like our children!"
But regional Deputy Prosecutor-General Nikolai Shepel said that if justice is to be done, the law must be observed.
"We must live only by the law. In order to combat terrorism, violations of the law, crime, we must live by the letter of the law," he said.
Kuliyev faces eight charges, including banditry, terrorism, murder, attempted murder, hostage taking, attempting to kill a law-enforcement officer, illegal weapons possession and car theft.
Kuliev admits he took part in the Beslan siege but denies shooting anyone, saying he only fired his gun in the air. Kuliev also denies prior knowledge of the operation, saying he thought the militants intended to seize a checkpoint.
The prosecution contends that Kuliev and his associates put into action plans drafted by notorious Chechen warlord Shamil Basaev and late Chechen leader Aslan Maskhadov. They also allege that a Saudi national called Taufik al-Jadani participated as well.
The fact that Kuliev was shown on television soon after his initial arrest, confessing that Maskhadov had ordered the school raid with the goal of starting a war in the whole of the Caucasus, is likely to complicate the defense's case.
Prosecutors plan to call 90 witnesses to testify on their behalf in the trial. No defense witnesses are expected.
The trial is expected to last several months, according to Deputy Prosecutor-General Shepel.
What is less clear is whether some of the unanswered questions about Beslan will ever be answered. They include the exact number of those killed, how it was possible for the militants to infiltrate the school and apparently store weapons there in advance -- and whether there could have been a chance to end the incident peacefully.
(RFE/RL's Russian Service contributed to this report.)