He was born August 13 1888 into a Ukrainian family. His father was a mining engineer or, according to other sources, a seminar teacher. Voykov became involved in revolutionary activity at a young age. Whilst still attending Gymnasium, Voykov fantasized about killing the Tsar.
For his underground activities, he was expelled from the sixth grade of the Kerch Gymnasium. His parents had to change their place of residence and work. The family moved to Keukeneiz, where his father settled himself as a road master in the estate of the landowner Alchevsky. Thanks to the efforts of his mother, Pyotr was accepted into the eighth grade of the Yalta Alexandrovskaya Men's Gymnasium, but from there he was soon expelled.
The exact date of Voykov's accession to the RSDLP is not known, but a period between 1903-1905 is assumed. Voykov was one of the five organizers and participants in the terrorist attack on July 20, 1906 against the police chief, M. M. Gvozdevich. The terrorist attack was unsuccessful; an improvised explosive device exploded 50 steps from the police station, and Gvozdevich was not injured. Voykov fled first to Kekeneiz, to his father, and then to Sevastopol and St. Petersburg. Two other participants in the terrorist act, Dmitry Nashaburgsky and Pyotr Koren, did not mention Voykov's name. The fact of Voykov's participation was established only in 1907.
In the summer of 1906 he joined the militant wing of the RSDLP, and participated in the transport of bombs, and the attempt on the life of Yalta Mayor General I. A. Dumbadze. In the autumn of 1906, at the height of the riots amid the revolution of 1905-1907, a State of emergency was declared in Yalta, and General Dumbadze authoritatively ruled the city, for which he was widely hated by socialists and militant revolutionaries. The latter demanded that the Mayor immediately resign, threatening him with death.
On February 26, 1907, a bomb was thrown from the balcony of Novikov's dacha, located near Yalta, onto a passing carriage carrying Dumbadze. The Mayor was concussed and scratched, and the driver and horses were wounded, but no one was killed. The terrorist, who belonged to one of the combat units of the Socialist-Revolutionary Party, immediately shot himself on the spot. As it turned out later, the organizer of the assassination attempt on Dumbadze was the 18-year-old Peter Voykov, who was expelled from Yalta a month and a half beforehand.