In a shocking turn of events, a deadly terrorist attack unfolded on Friday in a crowded concert hall near Moscow, claiming the lives of at least 115 people, with hundreds more left injured. State media reported on Saturday that Russian authorities have detained 11 individuals, including four suspected gunmen, in connection with the attack.

According to Russia's Investigative Committee, the four suspects were apprehended in the Bryansk region of western Russia, not far from the border with Ukraine. It was revealed that they had intended to cross the border into Ukraine and reportedly had contacts there. The arrests were briefed to President Vladimir Putin by the head of Russia's FSB, as stated by state news agency Tass.

Disturbing videos circulating on Russian social media depict scenes of chaos and terror inside the concert hall, connected to a shopping mall. Footage shows people screaming and taking cover while gunfire rattles incessantly. The attackers also set the venue ablaze, leading to a partial collapse of the building's roof.

Eyewitnesses recalled the harrowing moments of panic and desperation. Dave Primov, one of the eyewitnesses, told CBS News, "The shots were constant. People panicked and started to run. Some fell down and were trampled on."

The Islamic State group has claimed responsibility for the attack, an assertion backed by U.S. intelligence. The U.S. Embassy had previously issued a warning for Americans to avoid concert venues due to the threat of a terrorist attack.

Although the motive behind the attack remains unclear, it occurred shortly after President Putin secured a landslide victory in the elections, solidifying his control amid the ongoing conflict with Ukraine. The U.N. Security Council has strongly condemned the "heinous and cowardly terrorist attack" and stressed the importance of holding the perpetrators accountable.

Meanwhile, in a heartening display of solidarity, hundreds of Moscow residents lined up to donate blood and plasma on Saturday morning, as stated by Russia's health ministry.

This devastating incident marks the deadliest terrorist attack in Russia in recent years. The country had previously been shaken by a series of deadly attacks during the early 2000s when fighting with separatists in the Russian province of Chechnya was at its peak. These attacks include the 2002 Moscow theater hostage crisis that claimed the lives of 129 hostages and 41 Chechen fighters, and the 2004 Beslan school hostage crisis, resulting in the deaths of over 330 individuals, including many children.

As investigations continue, the focus now shifts to bring justice to the victims and their families, while the international community joins forces to combat the growing threat of terrorism.

CBS News' Debora Patta, David Martin, Andy Triay, and Olivia Gazis contributed to this report.