Update Oct 7, 2018:
Russian journalist, Sergey Dorenko, is claiming the pilot flying the helicopter had two bullet wounds, suggesting the helicopter crash killing Saak Karapetyan was actually an assassination. Dorenko is claiming there’s a government coverup in Karapetyan’s death. Russian authorities deny everything, claiming the helicopter clipped tree tops before crashing.
Karapetyan was supposedly going on a hunting trip when the helicopter crashed. The crash happened shortly before Russian operatives were apprehended trying to hack the wifi where an investigation into the attempted poisoning of Sergei Skripal and his daughter Yulia was taking place.

Saak Karapetyan was a Russian Deputy Prosecutor General who seems to have specialized in obstructing international investigations into crimes committed by the Russian state. By any means necessary.
This year it was uncovered that Karapetyan worked with Russian lawyer, Natalia Veselnitskaya, on a few projects related to sanctions against oligarchs. He and Veselnitskaya seemed to be focused on discrediting Bill Browder and his company, Prevezon.
Karapetyan was the Russian spokesperson who denied Russian involvement in the attempted murder of Skripal and his daugher, and a few other assorted assassinations attributed to Russia.
Karapetyan was killed in a helicoptor crash on October 3rd, 2018. It was an unauthorized flight, after dark, in bad weather. Nothing odd about his death at all.