MOSCOW -- Human-rights lawyer Stanislav Markelov told reporters Monday he would use all legal means to overturn the early release of the most senior Russian military officer ever convicted of war crimes in Chechnya. After walking out of the news conference, he was shot dead. A journalist with him was also killed.

The murder on a downtown Moscow street drew comparisons to the 2006 slaying of investigative journalist Anna Politkovskaya and threatens to stir anti-Kremlin sentiment in Chechnya, where Russia fought two military campaigns in a decade to quell separatist sentiment.

Mr. Markelov, 34 years old, represented the family of an 18-year-old Chechen girl, Elza Kungayeva, who was strangled to death in 2000 by Col. Yuri Budanov. Mr. Budanov was found guilty of the murder in 2003 and sentenced to 10 years in prison, including time served. The former colonel, who was stripped of his rank, was released for good behavior Thursday, 1½ years early.

After Ms. Kungayeva's murder, Mr. Budanov swiftly became a symbol to Chechens of Russian military brutality. Convicting him and making sure he served his full term became a matter of honor for Chechnya's pro-Kremlin leadership and tangible proof of the limited justice Russia grudgingly meted out to its own army.

Russian nationalists and many fellow servicemen saw Mr. Budanov as a hero who was unfairly persecuted for a crime committed in a war against a people guilty of similar atrocities against Russians. Mr. Budanov had said he thought the 18-year-old girl was a rebel sniper and that he killed her in a moment of insane rage.