From the Moscow Times:
No suspects had been detained as of Tuesday.
“According to witnesses, the killers were yelling, ‘Glory to Russia’ and ‘Long live Russia,’” said Simon Tsaturyan, the Sardaryan family’s lawyer.
Tsaturyan said the attackers pulled the train’s emergency lever after stabbing Sardaryan and fled the scene. Sardaryan died on the spot, Tsaturyan said.
Here.