The group said that Chepiga's military school listed him among graduates bestowed with the Hero of Russian Federation award in December 2014, adding that the data signaled that he likely received the medal for his actions in eastern Ukraine.
Two Russian men later appeared on the state-funded RT channel and made widely mocked claims that they only went to England in early March to visit the "wonderful town" of Salisbury and its famous cathedral. (Bellingcat/Supplied) Bellingcat said Colonel Chepiga was awarded Russia's highest state award, the Hero of the Russian federation in 2014.
The Russian Embassy in London was not immediately available to comment.
In early September, Mrs May named the two men as Boshirov and Alexander Petrov.
Chepiga appears to have no social media accounts and there are no photographs of him online, the Bellingcat and Insider report said.
British Prime Minister Theresa May has said that the men suspected of the poisoning were members of Russian military intelligence acting on orders from a "high level".
The group, Bellingcat, said Wednesday that the suspect, whose passport name was Ruslan Boshirov, is in fact Col. Anatoliy Chepiga, who in 2014 was awarded Russia's highest medal, the Hero of Russian Federation.
Britain has charged Boshirov and Petrov with trying to kill Skripal and his daughter on March 4 with the Soviet-designed nerve agent Novichok in the English city of Salisbury.
He was born on 5 April 1978 and graduated into the military following a stint at one of Russia's elite training grounds, the Far-Eastern Military Command Academy, according to Bellingcat.
Former Russian military intelligence colonel Sergei Skripal attends a hearing at the Moscow District Military Court in Moscow on August 9, 2006. The group eventually tracked down Chepiga's passport file, dated 2003, with a picture bearing a strong resemblance to Boshirov.
It had already been reported in Russian media that the passport numbers of the men are separated by only three digits (-1294 and -1297) meaning they were issued at nearly exactly the same time.
The pair survived the attack but two more people were poisoned and one of the victims, Dawn Sturgess, died in July.
Police have previously said they believed "Boshirev" and "Petrov" were aliases, not the men's real names.