A bomb blast tore through a trolleybus in Volgograd, Russia, on Monday, December 30, a day after a suicide bombing at the city's main railway station. Denis Tyrin/AP
An ambulance leaves the site of a trolleybus explosion. Denis Tyrin/AP
Experts, firefighters and police officers examine the scene of the blast. Denis Tyrin/AP
Police officers examine the area around the site of the explosion. Denis Tyrin/AP
A demolition expert walks among the wreckage. AP Photo/Denis Tyrin
Russian security forces stand guard outside a train station in Volgograd, following a suicide bomb attack on Sunday, December 29. STRINGER/AFP/Getty Images
A police officer guards the main entrance to the station. stringer/AP
Bodies lie covered on the ground as police continue to investigate the scene. STRINGER/AFP/Getty Images
Police investigators inspect debris at the scene of the explosion. STRINGER/AFP/Getty Images
An officer stands guard outside the station. STRINGER/AFP/Getty Images