The suspect in a recent bomb threat involving the presidential office arrived in Korea on Tuesday. He was residing in Europe.

The 20-something man was taken into custody for questioning, according to Gyeonggi Provincial Police Agency.

The suspect was confirmed Monday to be the son of a former aide to National Assembly Speaker Chung Ui-hwa.

Police said he called Cheong Wa Dae’s civil affairs office Sunday around 2:39 a.m. and threatened to bomb it.

“If you do not show me your willingness by noon, I will blow up Cheong Wa Dae,” he said in his message, without elaborating on what he meant by “willingness.”

He made similar threats on Jan. 17 on Twitter, saying he would bomb the residence of President Park Geun-hye and her Chief of Staff Kim Ki-choon.

His motives were not yet known as of Tuesday, but he is believed to have a history of mental illness.

The suspect was accompanied by his father, who on Friday submitted his resignation and headed to France to talk his son into facing authorities here. His father was a Grade-4 assistant at the assembly speaker’s office, and was in charge of arranging external events.

Investigators have yet to definitively comment on how plausible the suspect’s threat was, but said there was “very little possibility” that he would have been able to carry out the bombing.

The suspect left for France on Jan. 13 without his parents’ knowledge, and is unlikely to have had time to prepare the supposed attack. While Kang specified when of his attacks would take place, nothing actually occurred at the cited times.

“As of now, the bomb threats appear to have been a simple prank with no possibility of being carried out. But we cannot conclusively say so untill we’ve questioned him,” said a police official. Investigators are planning to ask Kang about his motives, whether he had any accomplices, his reasons for going to France and what he did there.

By Yoon Min-sik (minsikyoon@heraldcorp.com)