Piknik, a longtime Russian rock band, is now at the center of a tragedy.

Early Saturday, Piknik, one of Russia’s most popular heritage rock bands, published a message to its page on Vkontakte, one of the country’s largest social media sites: “We are deeply shocked by this terrible tragedy and mourn with you.”

The night before, the band was scheduled to play the first of two sold-out concerts, accompanied by a symphony orchestra, at Crocus City Hall in suburban Moscow. But before Piknik took the stage, four gunmen entered the vast venue, opened fire and murdered at least 133 people.

The victims appear to have included some of Piknik’s own team. On Saturday evening, another note appeared on the band’s Vkontakte page to say that the woman who ran the band’s merchandise stalls was missing.

“We are not ready to believe the worst,” the message said.

The attack at Crocus City Hall has brought renewed attention to Piknik, a band that has provided the soundtrack to the lives of many Russian rock fans for over four decades.

Ilya Kukulin, a cultural historian at Amherst College in Massachusetts, said in an interview that Piknik was one of the Soviet Union’s “monsters of rock,” with songs inspired by classic Western rock acts including David Bowie and a range of Russian styles.

Since releasing its debut album, 1982’s “Smoke,” Piknik — led by Edmund Shklyarsky, the band’s singer and guitarist — has grown in popularity despite its music being often gloomy with gothic lyrics. Kukulin attributed this partly to the group’s inventive stage shows.