The four suspects, who were detained the day after the incident, made their first appearance at Basman District Court in Moscow on Sunday and were declared to be in pre-trial detention. Photo: VCG

The Crocus City Hall, in Moscow, in ruins after the terrorist attack. Crocus International, the owner of the concert hall, expressed deep sorrow over the attack and said it would restore the building. Photo: IC Photo

Suspect Dalerdzhon Mirzoyev is escorted on Sunday at Basman District Court in Moscow. Four suspects have been arrested and could face life in prison. Photo: VCG

Russian President Vladimir Putin paid tribute to the victims of the terrorist attack on Sunday, declared a day of national mourning. Photo: VCG

Terrorists attacked the Crocus City Hall just before 8 p.m. on Friday during a rock concert. According to the latest statistics released by Russian authorities on Sunday, 137 bodies had been found at the scene including three children. Photo: VCG

Medical workers transport the bodies of victims of the attack at the concert hall, located in a northern suburb of Moscow on Friday. Photo: VCG

Reporters interview people near the Crocus City Hall after the attack Friday. Photo: VCG

A highway billboard displays an image of candles as the country mourned the victims of the attack. Photo: VCG