https://www.cnn.com/2020/05/04/europ...ntl/index.html
3 doctors so distraught they jumped out of windows after voicing their concerns.
He started very early as well.
https://www.theguardian.com/world/20.../kursk.russia3
These methods are done to silence opposition, and in a deliberate enough manner to show that these are intentional.
Think of Yagami Light of Deathnote and heart attacks. Putin sees himself as divine judgement and wants it known that he is in control.