Ilocos Norte Rep. Alexander "Sandro" Marcos said Friday that being the first signatory to the impeachment complaint against Vice President Sara Duterte should not come as a surprise, citing the latter's previous utterances of serious threats against his family.

In an ambush interview, Marcos mentioned that Duterte's threat to have the remains of his late grandfather, former president Ferdinand Marcos Sr., exhumed and dumped into the West Philippine Sea, as well as her alleged killing plot against his parents — President Ferdinand Marcos Jr. and First Lady Liza Araneta Marcos — and uncle, Speaker Martin Romualdez, prompted him to head the endorsers of the impeachment complaint.

"If [that] person said that she wants to exhume your grandfather['s remains] and throw the body in the West Philippine Sea, said she wants to kill the President and the First Lady who are my parents, and wants to kill the Speaker, then, why would people be even surprised that I signed?" he said in Filipino.

According to the Senior Deputy Majority Leader, such statements "can't be taken lightly, especially from someone with such a high position."

To recall, Rep. Marcos had criticized Duterte for "crossing the line," making him "disdain" her "abhorrent comments" against his late grandfather. He also suggested that the VP might need "mental clarity that seems to be eluding her."

In a press conference on Friday, Duterte vehemently denied that she uttered such a grave threat to the life of the President.

"I did not make an assassination threat to the President. They just say that. They just say there's an assassin, there's a gunman. I didn't say that," the VP argued.

Rep. Marcos, however, countered, “I think we know the truth to that. So let's just leave it at that.”

The alleged plot to have the country's top leaders killed was among the grounds for Duterte's impeachment by the House of Representatives on Wednesday.

With 215 votes, or more than double the required one-third votes (102 signatory lawmakers), Duterte became the first sitting second-highest official ever to be impeached by Congress. The number of petitioners is also likely to increase to 240 or more than 80 percent of the 306-member House by Monday.

Rep. Marcos admitted that his signature on the impeachment petition had the blessings of his father but denied spearheading the signature drive to fast-track the impeachment process.

"He said, 'Do your duty as a congressman and uphold your oath to the Constitution that you swore to protect.' And it is my constitutional duty to go through the impeachment process as an elected representative,” the lawmaker narrated.

He also dismissed the alleged "ayuda" given to lawmakers in exchange for their signatures, labeling it a "smear campaign" by pro-Duterte groups.

“[That is] to discredit the (impeachment) movement. You can't blame them. We knew who their boss is. But no, there was nothing offered in exchange for the signatures. I was there in the room. The articles of impeachment were actually discussed, and then people were given the choice to sign or not,” he explained.

The Senate is expected to try Duterte when Congress reconvenes after the 12 May elections.

The Senate will need a two-thirds vote, or at least 16 of the 24 sitting senators, to convict and remove Duterte from office. If convicted, Duterte will be perpetually disqualified from holding any public office in the future.