A terrifying pattern is slowly forming in Russia.
During rush hour Monday, a bomb detonated on a trolleybus, killing 14 people in the city of Volgograd. The day before, an explosion at the city's main train station killed 17 people and wounded dozens. In October, a bus blast that killed seven was caught on a driver's dashboard cam.
Volgograd, about 400 miles northeast of Sochi, has become a target for suicide bombings. The city is a major transportation hub for people traveling from Moscow and central Russia to Sochi, where the Winter Olympic Games will be held in February.
Volgograd also houses the rail station that leads to and from the North Caucasus, where Chechens and Russians—divided in religious, cultural, and political beliefs—have been locked in conflict for years. Chechen separatist groups from this region are usually the suspects in terrorist attacks in Russia, and the recent deadly attacks suggest they could just be getting started.
In July, the Chechen separatist group Caucasus Emirate, the organization suspected in Monday's bombing, released a video statement promising violence during the games. The Russians, said the group's leader Doku Umarov, "plan to hold the Olympics on the bones of our ancestors, on the bones of many, many dead Muslims buried on the territory of our land on the Black Sea, and we Mujahedeen are obliged not to permit that—using any methods allowed us by the almighty Allah."
The U.S. State Department considers the Caucasus Emirate a foreign terrorist group, and offers a $5 million reward for information about Umarov's location. The White House condemned the latest attacks in a statement Monday, announcing that it has offered its "full support" to the Russian government in security preparations for the winter games. "The United States stands in solidarity with the Russian people against terrorism," said National Security Council spokeswoman Caitlin Hayden.
Thomas Bach, president of the International Olympic Committee, said Monday he is "certain that everything will be done to ensure the security of the athletes and all the participants of the Olympic Games," according to the AP.
Still, the threat of more attacks, especially in Volgograd, has become real for citizens, spectators, and athletes. "Is this the beginning of a larger terrorist campaign leading up to Sochi?" wrote a pair of homeland-security and counterterrorism experts for ABC News on Monday. "There should be little doubt it is."