Lone Wolf?

Stepan Balmashev (1881-1902), son of a political exile from Arkhangelsk, got radicalised as a student at the University of Kiev.
On 15 April 1902 he committed the first terrorist attack of the Russian Socialist-Revolutionary Party (PSR) when he shot to death the minister of internal affairs Sipiagin.
That is to say, the attack was claimed by the Socialist-Revolutionaries, but others contested this and argued Balmasjev acted as a lone wolf.
Refusing to ask the tsar for pardon, Balmashev was hanged not much later.