SCOTT SIMON, HOST:

This is WEEKEND EDITION from NPR News. I'm Scott Simon. Mourners in Moscow are gathering at the site where one of Russia's most prominent dissidents was gunned down last night. Boris Nemtsov was a former deputy prime minister. He later became one of President Putin's fiercest critics. Police say that Mr. Nemtsov was walking on a bridge near the Kremlin when gunmen pulled up in a car and shot him to death four times in the back. NPR's Corey Flintoff joins us now from near the site where the shooting took place.

Corey, thanks for being with us and please tell us what you're seeing.

COREY FLINTOFF, BYLINE: Thank you, Scott. I'm standing on the end of a bridge where Boris Nemtsov was shot last night. I'm right behind a makeshift memorial where people are putting flowers. Some people are actually weeping as they heap up these flowers, and people are lighting little candles in jars. I would say there's probably 1,000 people strung out along this bridge come here to memorialize Boris Nemtsov. Nemtsov was one of the organizers of a major opposition march that was planned to take place tomorrow. We're hearing that that march has now been canceled and that the other leaders are asking people to find ways to memorialize Nemtsov instead, so that seems to be why many of them are coming here now.

SIMON: Boris Nemtsov was a bold opposition leader, but the opposition hasn't been particularly popular in Russia in recent years, has it? What makes him a target?

FLINTOFF: You know, it's hard to convey just how bold Nemtsov was when it coming came to criticizing President Putin. Just a few hours before he was killed last night, he gave an interview to an independent radio station here. It's called Echo of Moscow and here's a quote from that interview.

(SOUNDBITE OF ARCHIVED RECORDING)

BORIS NEMTSOV: (Foreign language spoken).

FLINTOFF: What he's saying is - and I'm quoting here - "the most important reason for the current crisis is that Putin started a mad, aggressive and deadly policy for our country and many citizens, a policy of war against Ukraine." Nemtsov vehemently opposed Russia's annexation of Crimea. He said Crimea was part of Ukraine. And just recently, he was said to be working on a report that he believed would prove that Russia was directly involved in the war in Eastern Ukraine. And that, of course, is something that the Kremlin has consistently denied.

SIMON: It's been reported that Vladimir Putin himself will oversee the investigation. Does this mean, as I think a lot of people have suggested, that the fox will be investigating a death in the chicken coop?

FLINTOFF: Well, it's hard to tell. One interesting thing about this crime is that it took place in one of the most thoroughly policed and surveilled areas in the world. The bridge here is within clear sight of the Kremlin surveillance cameras. There was at least one eyewitness. Nemtsov was with a female acquaintance, a young woman from Ukraine, when he was shot. She's being questioned. But you know, judging from the news video we saw from here last night, there wasn't much of an effort to secure the crime scene. So it's unclear what'll develop from this investigation. Police and various pro-Kremlin commentators have floated all kinds of theories, including that this is a contract murder that somehow involved organized crime, or that it was an act of Islamic terrorism. So, this is just getting more obscure by the hour.

SIMON: NPR's Corey Flintoff in Moscow, thanks so much.

FLINTOFF: Thank you, Scott. Transcript provided by NPR, Copyright NPR.