South Korean investigators on Friday pressed ahead with their probe into impeached President Yoon Suk Yeol over his Dec. 3 martial law declaration, issuing another summons demanding that he appear for questioning on Christmas Day,

South Korean police have questioned Prime Minister and Acting President Han Duck-soo as part of an investigation into the short-lived decision this month to impose martial law, an official at his office said on Friday.

The president faces an accusation of insurrection and, in a first for a sitting leader, the possibility of arrest. Here’s what to know about his political future.