The PM's bodyguards were it seems from the article outside this apt building at all times and only broke in when he did not answer a call - probably a wake up call that went unanswered? In any case a gas leak is not an uncommon thing in the former states of the USSR. Every year HUNDREDS maybe thousands die from gas leaks - some that lead to explosions of whole apt blocks.
I find it funny people scream "Putin did it" at the drop of a hat.