Suspects in the Russia concert hall attack, which left more than 130 dead, arrived at a Moscow district court on Sunday night.

There was a heavy police presence around the court, which is expected to determine pretrial restrictions for the men, who are suspected of opening fire on crowds of concert goers at the capital’s Crocus City Hall.

One of the suspects was led blindfolded into the courtroom. His blindfold was removed and a black eye was visible.

Friday’s attack, which has been claimed by an affiliate of the Islamic State group, is the deadliest on Russian soil in years.

Russian authorities arrested four suspected attackers on Saturday, with seven more detained on suspicion of involvement in the attack, Russian President Vladimir Putin said in a nighttime address to the nation, on Saturday. He claimed they were captured while fleeing to Ukraine, something that Kyiv firmly denies.

Family and friends of those still missing after an attack that killed more than 130 peopleat a suburban Moscow concert hallwaited for news of their loved ones as Russia observed a day of national mourning on Sunday.

Events at cultural institutions were canceled, flags were lowered to half-staff and television entertainment and advertising were suspended, according to state news agency RIA Novosti. A steadystream of peopleadded to a makeshift memorial near the burnt-out concert hall, creating a huge mound of flowers.

“People came to a concert, some people came to relax with their families, and any one of us could have been in that situation. And I want to express my condolences to all the families that were affected here and I want to pay tribute to these people," Andrey Kondakov, one of the mourners who came to lay flowers at the memorial, told The Associated Press.