There is absolutely no reason to believe this story, as it is almost certainly a very crudely made fake. The screenshots showing the RT "story" about Tsemakh's death are very simple fakes, and it's surprising that so many people fell for this. 
There are dozens of reasons why the screenshots are fake, but the most obvious ones: the sequential number in the URL doesn't fit stories published today, and also, just read the language from the final lines of the story. RT never writes like this, in Russian or English.
RT never published this story, and all the screenshots showing it are fake.
RT Russian doesn't have "Question More" on top. It says RТ НА РУССКОМ, and the media sharing bar has VK on it, unlike the fake screenshot.
Very disappointing that so many Ukrainian outlets fell for this.
RT Russian doesn't have "Question More" on top. It says RТ НА РУССКОМ, and the media sharing bar has VK on it, unlike the fake screenshot.
Very disappointing that so many Ukrainian outlets fell for this.
Note what the top-left (Question More / RT НА РУССКОМ) and top-right (social media sharing) sections of the page look like on the fake screenshot (first photo) and russian.rt.com in reality (second and third photos):
