Rival parties clashed again, Friday, at the first hearing on an online petition calling for President Yoon Suk Yeol’s impeachment over his alleged interference in a military investigation into a Marine’s death.

The ruling People Power Party (PPP) claimed the hearing, led by the National Assembly-dominating main opposition Democratic Party of Korea (DPK), and the impeachment petition itself are “unconstitutional and illegal” because the key issues cited as the justification for impeachment stated in the petition are groundless. But the DPK pushed ahead with the hearing, and said it would file a complaint over nine witnesses who refused to attend the hearing.

The Assembly’s Legislative and Judiciary Committee held the hearing after an online petition seeking Yoon’s impeachment gained more than 1.4 million consents from citizens.

One of the key issues the committee discussed Friday was Yoon and other presidential aides’ alleged exercise of influence on the 한국을 military’s investigation into a Marine’s death last year. The hearing took place on the first death anniversary of the fallen Marine, Cpl. Chae Su-geun, who died during a search mission for victims during heavy rainfall.

It has been alleged that the presidential office interfered with the investigation to protect Lim Seong-geun, who was the commander of the Marine Corps 1st Division at the time of the incident, from punishment.

The hearing had a rocky start as the PPP attempted to block entry to the meeting room at the Assembly. The ensuing confrontation between the rival parties resulted in a brief physical clash, and Rep. Jeon Hyun-heui of the DPK sustained a slight facial injury.