Public prosecutors on Friday moved to begin an investigation into Rep. Kim Sun-dong, who set off tear gas inside the parliamentary chamber, following a complaint filed by civic groups.

“The probe will soon begin, centering on allegations stated in the complaint,” an official at the Supreme Prosecutors’ Office said.

Rightist civic groups, including Right Korea, filed a complaint against Rep. Kim, accusing the lawmaker of the far-left Democratic Labor Party of committing several crimes, including contempt of parliament, special obstruction of public duty and possession of an illegal weapon.

Investigators said they plan to first secure video recordings of the voting session, which was closed to the public and even to the media.

Rep. Kim detonated a tear gas canister during a parliamentary vote on the Korea-U.S. Free Trade Agreement on Tuesday.

Violence has erupted at the National Assembly before, but it was first time that a tear gas grenade was set off inside the chamber. Previous cases involved chainsaws and hammers.

Faced with mounting public criticism, the ruling Grand National Party pressured Rep. Kim to resign, saying the incident was tantamount to an “act of terrorism” and that the lawmaker doesn’t “qualify” to be a member of the parliament. Despite the harsh words, none moved to bring legal action against Kim.

Rep. Kim is granted by law certain immunities for his action and speech inside the parliament, but that doesn’t cover tear gas bombing, prosecution officials said.

Contempt of parliament is punishable by up to 3 years in jail and a fine of up to 7 million won. Special obstruction of public duty carries a harsher penalty of a maximum four and a half years’ imprisonment.

The tear gas canister detonated by Rep. Kim was manufactured in 1985 for use by police. Prosecutors plan to investigate how the lawmaker came to possess it.

By Lee Sun-young (milaya@heraldcorp.com)