A serviceman in Russian-held Crimea opened fire on fellow soldiers and civilians, killing four people and wounding four, the Moscow-installed governor of Sevastopol said Tuesday.

The shooting occurred in the village of Khmelnytske, which is part of Sevastopol, said Gov. Mikhail Razvozhayev, without specifying when exactly it happened.

The serviceman initially opened fire at fellow soldiers, killing one and wounding another, Razvozhayev said, adding that he then killed three civilians and wounded another three people.

The gunman, who was not identified, was detained and law enforcement was investigating the incident, he added, although he did not elaborate on a possible motive for the shootings.

Crimea was illegally annexed from Ukraine by Russia in 2014. The peninsula on the Black Sea holds strategic importance for the Kremlin in its full-scale invasion of Ukraine, now in its fifth year. Russian troops that were concentrated in Crimea quickly seized large parts of southern Ukraine early in the war and secured the land route to the peninsula.

In recent months, Ukraine has attacked Russian supply lines to Crimea, causing severe fuel shortages on the peninsula, which is a magnet for tourism during warmer months.