So far, the Russian government has not produced any evidence that the four men arrested in connection with carrying out the attack had any links to Ukraine. Russian officials and pro-Kremlin media outlets have cited the site of their arrest — the Bryansk region of Russia, which borders Ukraine — as evidence that they were planning to flee there.
On Saturday, Mr. Putin claimed that according to preliminary information, “a window was prepared for them on the Ukrainian side to cross the state border.”
At the meeting with Mr. Putin on Monday, Russian officials provided more details about how the tragedy had unfolded.
According to Aleksandr I. Bastrykin, Russia’s top investigator, the four suspects arrived at the scene more than an hour before the concert. They waited for the spectators to gather and started shooting two minutes before the show was scheduled to start, said Mr. Bastrykin, who is the head of the Investigative Committee, Russia’s equivalent to the F.B.I. Thirteen minutes later, they fled the concert hall, Mr. Bastrykin said.
While leaving the parking lot in a white Renault, they ran over a family, severely injuring two children, he said. Investigators discovered two AK-47 rifles at the scene of the crime, the investigator said, as well as more than 500 bullets.
Tatiana A. Golikova, Russia’s deputy prime minister in charge of health care, said that 145 people were hospitalized in the aftermath of the attack and that 93, including five children, remained hospitalized. Nine people, including one child, are in very grave condition, fighting for their lives, she said.