Samsung heir apparent Lee Jae-yong was questioned by special investigators as a bribery suspect Thursday, putting not only himself, but also the tech giant deeper into the quagmire that centers on the corruption charges of President Park Geun-hye and her longtime friend Choi Soon-sil.

Surrounded by the press and hundreds of protestors, the vice chairman of Samsung Electronics, the world’s largest smartphone and chipmaker, entered the special investigation team’s office in southern Seoul at 9:30 a.m., saying that he was sorry for disappointing the people.

“I deeply apologize to the people for failing to show a positive image,” said Lee as he walked into the office. He did not respond to reporters asking whether he was requested by Park to support Choi in exchange for business favors.

The special counsel believes that Samsung gave money to Choi in return for Park or her former aides pushing the state-run National Pension Service to approve a controversial merger between two Samsung affiliates in 2015, a landmark deal widely seen as a step to speed up Lee’s succession. It also suspects that Lee may have known Choi’s close connection to President Park and tried to take advantage of it.

Investigators have been zeroing in on a 22 billion won ($18.6 million) contract signed by Samsung Electronics and a Germany-based company launched by Choi and her horse-riding daughter Chung Yoo-ra in 2015, questioning the contract’s role in Samsung’s merger. They arrested Moon Hyung-pyo, chief of the NPS and former health minister, last month over his role in the merger deal.

Summoning Lee appears to signify that the special investigators are in the final stage before targeting President Park.

To prosecute Park on bribery charges, investigators must identify a specific person to whom Park allegedly asked for money in exchange for favors for her friend Choi. This means that without discovering Lee’s wrongdoings, investigators may find it difficult to press charges against the president.

In November, Lee, along with other chaebol owners, was also summoned by state prosecutors as a witness to the alleged corruption charges involving Park and Choi. Lee and others, however, were referred to as “victims” who donated the money under pressure from the president.

In a show of confidence, special investigators said that, this time, they are open to the possibility of seeking an arrest warrant for Lee after the questioning. On Wednesday, they also requested lawmakers to file a suit against Lee for delivering false testimonies last month at a parliamentary hearing on the corruption scandal so that they can investigate him on charges of perjury as well, said Hong Jung-seok, a spokesman for the special prosecutors.

At the legislative hearing, Lee denied that Samsung’s contribution to Choi’s organizations were in return for business favors and said that the merger between Samsung C&T and Cheil Industries had nothing to do with his succession but was based entirely on managerial decisions.

The independent investigators have also reportedly secured circumstantial evidence of Park directly requesting Lee to support Choi and her family, contradicting the Samsung heir’s previous parliamentary testimony that claimed he did not know who she was.

In a surprise move, investigators said Choi’s niece Jang Si-ho recently turned in a tablet computer used by Choi. Jang has also reportedly confessed that she drafted a proposal seeking Samsung’s financial support for young athletes, a day before President Park met the Samsung heir in a one-on-one meeting on Feb. 15 last year. The proposal was delivered to Park through her close aide Chung Ho-sung, according to reports.

Meanwhile, investigators are reportedly gearing up for the probe into other conglomerate owners including SK Group Chairman Chey Tae-won.

The team has secured a recording of a conversation between Chey and Vice Chairman Kim Young-tae. At this time, the SK Group chairman was serving a prison term.

In the recording, Kim delivered President Park’s message that she would pardon him if he would support the Mir and the K-Sport foundations, two private organization launched by Choi. The SK Group chairman was released in August 2015, as Park granted him a presidential pardon.

By Cho Chung-un (christory@heraldcorp.com)