Boris Nemtsov at a rally in support of prisoners of the Bolotnaya square case, 21 February 2014. Photo by Ilya Schurov. CC BY 2.0 via Wikimedia Commons

Boris Nemtsov, a prominent opposition politician, former Russian deputy prime minister, and one of Vladimir Putin's top critics, has been shot and killed in Moscow. The murder took place in downtown Moscow, minutes from the Kremlin, on a bridge south of the Red Square.

Ilya Yashin, another opposition politician, was the first to confirm Nemtsov's death on Twitter.

Немцова застрелили. Он мертв.

— Илья Яшин (@IlyaYashin) February 27, 2015

Nemtsov has been shot. He is dead.

Journalists and activists were the first to arrive at the scene.

Фотография нашего корреспондента с Большого Каменного моста, места убийства Бориса Немцова pic.twitter.com/1rEW3KobXy

— Медиазона (@mediazzzona) February 27, 2015

A photo from our reporter from the Bolshoy Kamenny bridge, where Boris Nemtsov has been killed.

Just hours before his death, Nemtsov appeared on the Ekho Mosvky radio station to promote a Sunday march that he was supposed to lead with other opposition members to protest the Kremlin's handling of Russia's economic crisis and the conflict in Ukraine.

As the RuNet learned about the tragic event, many were shocked and saddened. Fellow politicians, journalists, and commentators expressed their condolences and shared recollections of Nemtsov. Some also commented on the possible motives for the killing.

There's an opposition march on Sunday. Navalny has been put in jail so he'd miss it. Then they went and shot Nemtsov.

— Julia Ioffe (@juliaioffe) February 27, 2015

Не просто оппозиционера, бывшего вице-премьера убили.

— Tatiana Souvorova (@tsuvorova) February 27, 2015

They didn't just kill an opposition figure, they killed a former deputy prime minister.

Journalist and opposition member Ksenia Sobchak shared memories of Nemtsov.

Знала его хорошо и очень любила. Он обожал жизнь,был настоящим демократом очень порядочным человеком.

— Ксения Собчак (@xenia_sobchak) February 27, 2015

I knew him well and loved him very much. He adored life, was a true democrat, and a very decent person.

Opposition Duma deputy Dmitry Gudkov and journalist Sergey Parkhomenko thought the intolerance of state propaganda was at least partly to blame for the tragic event.

Однозначно политическое убийство. Даже если не по заказу, то в результате той ненависти, которую пропагандировала наша власть

— Дмитрий Гудков (@gudkovd) February 27, 2015

An obvious political killing. Even if this was not a contract hit, it was a result of the hate propagated by our authorities.

А кто-то думал, это истерическое безумие, которое год уже нагоняет госпропаганда, – оно даром пройдет?

— Serguei Parkhomenko (@Sparkhom) February 27, 2015

Did anyone think the hysterical craze that the state propaganda has been generating for a year was just going to dissipate?

Opposition leader Garry Kasparov, who now lives abroad, expressed his condolences as well.

Devastated to hear of the brutal murder of my long-time opposition colleague Boris Nemtsov. Shot 4 times, once for each child he leaves.

— Garry Kasparov (@Kasparov63) February 27, 2015

The US ambassador to Russia, Michael McFaul, was equally stunned by the death.

Nemtsov was a real patriot, who believed in the possibility of Russia's greatness. I cry now both for his family & the country he so loved.

— Michael McFaul (@McFaul) February 27, 2015

Vladimir Putin has reportedly said Nemtsov's death “bears all the marks of a contract killing” and was likely intended to stir unrest or damage the Kremlin's reputation. According to his press secretary, Putin has personally ordered the heads of the Investigative Committee, the Federal Security Service, and the Ministry of Internal Affairs to oversee the investigation into the murder. Other political forces, including members of the Russian Communist party and LDPR, have also called the killing “a provocation” aimed at destabilizing the political situation and hardening “anti-Russian sentiment.”

A little over two weeks ago, in an interview with Sobesednik.ru, Nemtsov said his mother feared for his life, worrying that Putin might have him killed. (Nemtsov said he wasn't as panicked as his mother.) According to colleague Ilya Yashin, Nemtsov was working on a report about the involvement of the Russian military in the conflict in Ukraine. Nemtsov's lawyer, Vadim Prokhorov, said the politician recently received several death threats over social media.

After the police removed the body from the scene, Muscovites started bringing flowers to the bridge.

первые цветы вот. и лужа крови прямо на тротуаре. pic.twitter.com/7mdtZ7pfKy

— Егор Максимов (@egor_mq) February 27, 2015

here are the first flowers. and a puddle of blood right there on the sidewalk.

The organizers of the March 1 opposition rally have already said they're canceling the rally and holding a memorial in downtown Moscow, instead. There are already plans to appeal to city officials for a permit, though the mayor's office has been less than accommodating in the past.