A Russian politician who happened to be one of the most prominent critics of leader Vladimir Putin was shot dead in Moscow on Friday, just outside the Kremlin, the BBC reports

Boris Nemtsov was reportedly walking across a bridge when an unidentified gunman shot him four times in the back from a passing car.

The Kremlin released a statement saying that Putin condemned the killing and plans to personally oversee the investigation into Nemtsov's death.  

Nemtsov, who was a leader in Russia's post-Soviet Union economic reforms of the '90s under Boris Yeltsin, had reportedly fallen out of favor with Putin, in part because of his strong opposition to the war in Ukraine. 

Nemtsov had previously said he feared Putin would have him killed because of that opposition.