At the end of January, an executive at the Russian oil company Gazprom is found dead with his wrists cut.

Next to him lay a suicide note.

In February, the head of finance and security at Gazprom is found hanged.

It is also being investigated as a suicide.

Then it rolls on.

Several of the oligarchs and senior managers found dead have connections to the oil industry.

One is hung from a railing in his garden, one falls out of a hospital window, several are found shot, one drowns after falling off his motorboat, and one falls down a very long flight of stairs.

Another suffers a heart attack after being treated by shamans for a hangover - with frog poison.

"Is there a pattern"

In total, there may be at least 14 deaths.

According to SVT's Russia correspondent Bert Sundström, there are remarkably many, but it is not likely that all of them would be contract killings. 

- But some may really be, he says.

Bill Browder is convinced that in several cases it is about planned murders.

- There are not this many (deaths) in the oil and gas industry in one year without there being a pattern, he notes.

Bill Browder was a successful businessman in Russia who fell out of favor after starting to investigate corruption.

His lawyer was imprisoned and died.

Now he is an active Putin critic and human rights activist.

Struggle for money and power

Bill Browder says that right now there is a huge struggle for money and power in the oil and gas industry in particular, as the sanctions have affected other parts of the Russian economy.

- Oil and gas are areas where money still flows, says Bill Browder. 

According to him, the government is directly involved in the deaths, because politics and economics are so closely connected in the country.

- The government is not only aware of what is happening, but is behind it.

Bert Sundström expresses himself more cautiously.

- It cannot be ruled out that the state and the security services have a hand in the game, he notes nonetheless.

In the video, you hear more from Bill Browder about what could be behind the deaths

.