A bomb attack in Crimea has reportedly killed a former Ukrainian submarine commander who defected to Russia in 2014 when Moscow annexed the peninsula.

Russian authorities said a Russian military officer had been killed in a targeted attack in Sevastopol, Crimea’s biggest city, and that a woman has subsequently been arrested on suspicion of carrying out the attack. They did not name the officer targeted.

However, unofficial Telegram channels identified the officer as Robert Shageev who they say is a former commander of Ukraine’s only submarine, the Zaporizhzhia, and who switched allegiance to Russia in 2014 when Moscow annexed Crimea.

Back in 2014, a Ukraine defense ministry spokesperson told CNN that the Zaporizhzhia had been taken over and placed under the flag of the Russian naval fleet when its commander abandoned it.

The suspect was acting “on instructions from Ukrainian intelligence agencies,” Sevastopol’s governor Mikhail Razvozhayev said on Telegram. Ukraine has not publicly commented on the attack.