Good time of day, humans!
At 11:10 am Moscow time on November 7, 1990, Soviet Central TV suddenly interrupted its direct broadcast from Red Square, where an October Revolution anniversary parade was taking place, and started a classical music concert. Fifteen minutes later, the broadcast was resumed without comment.
In the evening of the same day, Vremya news dryly noted that security had detained «an inhabitant of Leningrad who had twice fired into air from a hunting rifle». A similar note was published in newspapers.
Most details of the incident became known only years later.
The gunman, 38 years old Alexander Shmonov (Александр Шмонов) did in fact plan to kill Gorbachev, but militsiya and plainclothes security men tackled him1. Whether he had a realistic chance of hitting Gorbachev at a distance of about 50 meters from a sawed-off shotgun2 or not, is still a matter of some debate in the Russian segment of the internet.
What if he succeeded? Disintegration of the Soviet Union was probably already irreversible at that point but it could have taken a slightly different path.
Although he insisted he was sane, Shmonov was subjected to several years of forced psychiatric treatment (likely one of the last victims of Soviet repressive psychiatry), and then released.
Now 72 years old, Shmonov presumably still lives in St. Petersburg, has a Xitter account with 2 (sic!) followers which he fairly recently used to spam the following (PSA: read at your own risk):
To Kill Gorbachev (In Russian)
On a side note, apart from being sawed off, the gun was acquired legally, and Shmonov had a permit for it.