When the robbers kill the US Marshalls and steal the painting the sound of suppressed gunshots is heard, however neither of the shooters have suppressors on their guns.
When Polina is making the statement her father forced her to do, she says her name is Polina Sarkov. That is incorrect, as in Russian her last name would have a feminine ending and would thus would be Sarkova.
Sarkov is clearly a man's last name, in Russian.