 What happened in Moscow could happen in U.S. Senator Marko Rubio, last Friday's terrorist attack at the Kroger City Hall music venue outside Moscow showed that Islamic State extremists have been able to re-establish their operations in Afghanistan after the chaotic U.S. pullout in 2021, Florida Senator Marko Rubio told ABC News. Last week, four gunmen stormed the arena just before a concert by the rock band Picnic. The venue, which has an estimated capacity of 7,500, was almost full. The terrorists killed the unarmed guards, opened fire on visitors, and then started a blaze which quickly spread through the building. At least 137 people were killed and over 180 were injured, according to officials. Speaking to ABC's This Week, Rubio said the fact that ISIS Qorasan, a wing of Islamic State based primarily in Afghanistan, has claimed responsibility for the atrocity suggests that the group has regained its footing and could be planning other attacks. ISIS K reconstituted itself as we warned would happen. When we had this disastrous withdrawal from Afghanistan, the senator said, recalling that one of the main criticisms of U.S. President Joe Biden's rushed exit was that it would give terrorists operating space to reorganize themselves. Once we leave Afghanistan and we're no longer there to conduct regular strikes, they can now operate openly. No matter how much the Taliban wants to take them on, they can't. They don't have the capability to do it. Rubio said, adding that Islamic State has now found a place to operate from and is likely looking for more real estate where they can organize and plot attacks. Rubio pointed out that in recent years, Islamic State extremists have carried out numerous attacks in Afghanistan and Iran and warned that the massacre on Russian soil means that they could soon attempt something similar in the U.S. Their aspirations go beyond Russia and Iran. The senator said adding that Islamic State would love to do what they did in Moscow here inside the United States. He stressed that the U.S. should be very concerned about such a threat and suggested that Islamic State extremists may use trafficking networks to enter the country through the U.S.-Mexico border.