Russia's investigative committee said that the 62-year-old suspect got into a cab driven by the 38-year-old victim along with three barrels of hard liquor, RIA Novosti reported.
The suspect then accused the driver of taking him to a police station instead of his home. He then had the driver pull over, accused him of being a police informant, and threw a live grenade at him.
"The passenger rushed out of the car, took off the clothes that bore traces of the crime and ran in the direction to the city," a statement from the investigative committee said.
The suspect, who was under investigation for illegal alcohol sales, was later detained by the police.
An investigation is underway.
The victim died Sunday from the injuries he suffered during the grenade blast.