A 66-year-old man shot dead three people in a shopping district in the southern Russian city of Krymsk on Thursday before killing himself, local authorities said.
At least two of the victims were known to the assailant, the local branch of the Investigative Committee, which probes major crimes in Russia, said in a statement posted on social media.
Early indications suggested that the gunman had shot the two acquaintances "out of personal hostility", it said. The identity of the third victim, a man, was still being established.
A 61-year-old man who was wounded was taken to hospital.
Footage circulating on social media showed a man firing as he walked down a street. At the end of the video he fires from close range at someone lying on the ground. The footage could not be verified.
Krymsk is a small city in Russia's southern Krasnodar region near the Crimean peninsula, which Russia unilaterally annexed from Ukraine in 2014.