(JTA) — Russian dissident Mikhail Khodorkovsky said the murder of former deputy prime minister Boris Nemtsov risked plunging Russia into civil war.

An unidentified shooter on Saturday gunned down Nemtsov, who was a Christian but said he had Jewish ancestry.

Khodorkovsky, a Russian Jew who left to Switzerland in 2013 after being sentenced to 11 years in prison in graft trials that critics alleged were designed to eliminate his political ambitions and criticisms of human rights abuses by Russian President Vladimir Putin, made the warning in a statement posted on Feb. 28 on his website.

“They’ve murdered Boris a hundred meters from the Kremlin,” Khodorkovsky wrote in the statement in reference to the gunning down that day of Nemtsov – a leading Russian opposition politician who died hours after appealing for support for a march on Sunday in Moscow against the war in Ukraine.

An unidentified attacker in a car shot Nemtsov four times in the back as he crossed a bridge in view of the Kremlin, police said. Putin condemned the murder and said he has was closely monitoring the investigation amid widespread speculation that Nemtsov was eliminated by the Kremlin, as were other dissidents before him.

“I know that for many people Boris’s death will become so much of a Rubicon that the entire country may become different,” Khodorkovsky wrote. “Will we find ourselves standing even closer to the precipice of all-out war of everybody against everybody? Or will we find within ourselves the strength to understand that political differences are not a reason to stop acting like human beings?”

Leonid Bershidsky, a Russian Jewish journalist, wrote that Nemtsov’s death validated Nemtsov’s criticism of Putin “in the most terrible way” in an Op-Ed he published on bloombergview.com.

He also criticized Putin’s government for what he said amounted to incitement against Nemtsov, whose name was “on every list of traitors published on the Internet and aired on state TV,” Bershidsky wrote. “It did not help that he was Jewish. There was a strong undercurrent of anti-Semitism in the smear campaign,” Bershidsky added.