Not far outside St. Petersburg, police have detained Alexey Stepan, a mine expert who formerly served in a separatist tank battalion in Luhansk. When apprehending him, officers discovered on his person a grenade and a stash of TNT, according to the news website 47news.ru.

The arrest reportedly took place on July 16, when a special police unit dedicated to countering extremism found in Stepan’s car 200 grams of TNT, a fragmentation grenade, and a firearm. He was later detained near the entrance to a local psychiatric hospital.

According to 47news.ru, this isn’t the first time police have detained Stepan. Just last month, in June 2015, he was also arrested at an apartment he was renting. Officers found in his home a pistol, ammunition (for both the pistol and a Kalashnikov), ten professional detonators, and 1.5 kilograms of C-4 explosives. Police charged him with illegal possession of deadly weapons and ammunition, but the court refused to jail him.

Citing one of Stepan’s compatriots from his unit in Luhansk, 47news.ru says he fought in Ukraine from October 2014 to April 2015.

On February 15, the most recent ceasefire took effect in eastern Ukraine. The agreement—signed in Minsk on February 12 after tense negotiations between the leaders of Ukraine, Russia, Germany, and France—calls for a complete ceasefire and the gradual withdrawal of heavy weapons from forward positions.