He's the second in command of the GRU - he would be a priority target for the GUR and would not go anywhere without a bodyguard somewhere near.
Assassins of any origin have life plans too, they don't want to be pinned down into a firefight with people who have lots of backup coming fast. The assassin did his job, which may yet prove successful, and did his best to get out fast.
This seems very likely to be true.