When the siege ended on 3 September in a chaotic and bloody battle between the militants and Russian forces, more than 330 people were dead -- including 186 children.
The tragedy drew unanimous condemnation worldwide.
German Chancellor Gerhard Schroeder called the hostage takers "terrorists without conscience who tried to reach political goals by murdering people."
Chechen separatist leader Aslan Maskhadov also condemned the siege and its alleged mastermind, radical field commander Shamil Basaev.
Maskhadov, who has since been killed by federal forces, said he would put Basaev on trial once the war with Russia had ended.
Most world leaders expressed solidarity and sympathy with Beslan residents and the government of Russian President Vladimir Putin.
But some, like European Commission President Romano Prodi, called on Moscow to clarify what he called the "many gray areas" surrounding the circumstances that led to the massacre.
A year later, there are still more questions than answers about what happened in Beslan. Who were the hostage takers? How many were there? Why were the Russian forces unable to prevent such a huge loss of life?
The Russian Prosecutor-General's Office is conducting the official probe into the hostage crisis.
Two parliamentary commissions -- one in Moscow and one in North Ossetia -- have also been investigating last year's bloody events.
In addition, Beslan residents are conducting their own separate probe. They have expressed anger at the government's lack of progress on the investigation.
The deputy speaker of the North Ossetian parliament, Stanislav Kesaev, is leading the regional legislative inquiry. He told RFE/RL's Russian Service he disagrees with many aspects of the official probe.
"[Without going into too many details], if there really were two women among the hostage takers, [as investigators say], why is it that some body parts found [in the rubble of the Beslan school] indicate that there was a third woman?" Kesaev asked. "Most importantly, we have the testimonies of the victims. One schoolteacher told investigators there were at least 50 hostage takers. When asked how could she know, she said her eyes were accustomed to counting [children]."
Prosecutors say there were officially 32 hostage takers, only one of whom was taken alive.
Nurpashi Kulaev, described as a 24-year-old Chechen carpenter, is currently on trial in North Ossetia's Supreme Court. He faces life in prison.
Kulaev is said to have made several conflicting statements, and many witnesses have reportedly been unable to identify him.
But Russian Deputy Prosecutor-General Nikolai Shepel told RFE/RL's Russian Service he has no doubt Kulaev was among those who conducted the siege.
"[Kulaev] is trying to make us believe he took almost no part in the raid, that he was forced to join the commando because of his elder brother, and that he didn't even know where they were heading," Shepel said. "He says he suspected they were about to commit a terrorist act, but not against a school. We believe he was one of the commandos and that, as a survivor, he must pay for the others in accordance with the Criminal Code of the Russian Federation."
In an interview broadcast last month on the U.S. television network ABC, Basaev admitted to helping plan the school siege. But he said he had ordered the lead hostage takers to unconditionally release all children under the age of 10 after handing Russian officials his demands.
Immediately after the crisis, Russian independent journalists and rights campaigners accused the Kremlin of misleading the public by saying the hostage takers had no demands and were unwilling to negotiate the release of any of the hostages.
Later, however, it surfaced that Moscow had refused to enter into talks with the militants, who were demanding that Russian troops withdraw from Chechnya.
In an interview with Russia's "Izvestiya" on 25 August, former North Ossetian President Aleksandr Dzasokhov said Russian security officials had threatened him with arrest if he went to the school to meet with the hostage takers.
The Kremlin also turned down a mediation offer by Maskhadov, and ordered the arrest of several of his relatives.
But it is the circumstances that led to the deaths of more than 330 people that has raised the most questions.
Authorities maintain they had no plans to storm the building, and that the assault was launched at around 1 p.m. local time, after the militants detonated booby-trapped bombs positioned in the gym. By that time, the hostage takers had reportedly already killed up to 21 adult male hostages.
In the interview broadcast on ABC, Basaev said the first exploding device went off when a Russian sniper shot a militant who was keeping his foot on the detonator of one of the booby-trapped bombs.
Russian officials say that once the assault began, the militants began shooting fleeing hostages in the back. They also blame the booby-trapped bombs for setting the school's gym ablaze and causing its roof to collapse on the hostages still inside.
But former hostages and other eyewitnesses have suggested that most of the civilian casualties were caused by heavy weaponry used during the Russian rescue operation.
Russian Deputy Prosecutor-General Shepel described the charges as groundless.
"The investigation has shown that troops received the order to use heavy weapons after 18:00, when there were no hostages left in the school and the militants were still putting up fierce resistance," Shepel said. "To avoid further losses, the troops were ordered to use heavy weapons."
The London-based Institute for War and Peace Reporting this month quoted investigators in North Ossetia as complaining about the absence of forensic ballistic experts in the wake of the siege. Such experts, they say, could have helped determine whether some of the hostages were killed by stray Russian bullets.
Shepel insisted that federal troops cannot be blamed for any of the civilian casualties.
"More than 300 people died before or during the blasts [detonated by the hostage takers]," Shepel said. "In other words, the [rescue] operation had nothing to do with that. Some people say our special forces shot down children. This is absolutely untrue. This is blasphemy."
In his interview with "Izvestiya," former North Ossetian President Dzasokhov said Putin wanted priority given to saving the lives of the hostages.
But rights campaigner Lidya Grafova, who was in Beslan during the crisis, charges that Russian authorities did not give enough thought to the consequences of an assault.
"What the schoolchildren's parents feared most was that the security forces would storm the building," Grafova said. "The prevailing mood [among officials] was to 'bump off' the terrorists -- not to save such an enormous number of children and adults at any cost. I'm still haunted by the image of this woman [I saw afterward] sitting in the school gym. She was holding the pictures of two of her relatives in her hands, swaying back and forth and crying, ‘The terrorists made them suffer and our soldiers burned them.'"
Following Dzasokhov's resignation last June, the North Ossetian legislature appointed its speaker, Beslan-born Taimuraz Mamsurov, to rule the republic.
Mamsurov, whose daughter was severely injured during the school drama, has promised to shed light on last year's bloodbath.
Few in North Ossetia, however, believe he will be able to meet his pledge.
(RFE/RL correspondents Yurii Bagrov and Mikhail Selenkov contributed to this report.)
Visit Remembering Beslan for RFE/RL's full coverage of the anniversary.