Washington (CNN) A bipartisan group of lawmakers and activists on Wednesday gathered on Capitol Hill to urge the administration not to let an American man's death in Egyptian custody be in vain.

Mustafa Kassem died of heart failure in the midst of a hunger strike after more than six years in an Egyptian prison.

At the press event organized by The Freedom Initiative, Human Rights Watch, Project on Middle East Democracy (POMED), Pretrial Rights International, and The James W. Foley Legacy Foundation, speakers expressed outrage at the 54-year-old's death -- which many referred to as a killing -- and called for the administration to punish the Egyptian regime for the crime.

'A tragedy that never ever should have happened'

"He died in an Egyptian prison for no reason whatsoever," said Sen. Patrick Leahy, a Vermont Democrat. "I'm a former prosecutor. I would call his death a homicide. It was as preventable as his imprisonment was unlawful."

"This is a tragedy that never ever should have happened and we as Americans should never, ever condone it," Leahy said.

Aya Hijazi, a US citizen formerly held as political prisoner in Egypt, said it was a nightmare come true.

"With Kassem's death, I feel that it could have been me," Hijazi said, describing how at the time she was arrested, it was made clear to her that it was because she was American.

"In a symbolic gesture, the officer stomped on my American passport and said, 'Show me what they will do,'" she recalled.

'We need to do better'

Lawmakers and activists who spoke at the event on Wednesday slammed the White House for not having done more to pressure Egypt to release Kassem.

"Aya and I -- again, under two different administrations -- are living testaments that the United States government has leverage it simply chooses not to use or uses at its will," former political prisoner Mohamed Soltan said. "In Mustafa's case, it did not use it. And it should. We need to do better. We need to do more. This is not okay."

Vice President Mike Pence and Secretary of State Mike Pompeo had both spoken out about the US citizen's detention.

However, when asked by CNN on Thursday for the administration's reaction to Kassem's death, counselor to the President Kellyanne Conway said, "I'm not aware of that so I don't want to talk about that. I just heard it from you."

The US State Department confirmed his death on Monday, with top senior State Department official David Schenker saying, "his death in custody was needless, tragic and avoidable."

Democratic Sen. Chris Van Hollen of Maryland accused the administration of giving "lip service to the unlawful detention of Mustafa Kassem and other Americans unlawfully in Egypt," but not doing anything else.

"And clearly President Sisi and the Egyptian regime have not gotten the message," Van Hollen said. "What they have seen is President (Donald) Trump rolling out the red carpet for President al-Sisi last year at the White House and President Trump calling al-Sisi, and I quote, 'my favorite dictator.'"

Trump hosted the Egyptian President Abdel Fattah al-Sisi -- who is notorious for human rights abuses -- for the second time in April 2019 , saying he was doing "a great job."

Van Hollen noted that the administration had used its authorities to punish Iranian officials for the detention of Americans there and should do the same in regards to Egypt, urging them to apply sanctions authorized by the Foreign Operations Appropriations Bill and the Global Magnitsky Act.

'The time to look the other way is over'

This call for sanctions or other punitive measures was echoed by other lawmakers of both parties at the event.

"There are times that cry out for action -- this is one of them," said Rep. Peter King, a New York Republican who counted Kassem as a constituent. He said the death of an American was not "a partisan issue."

"I am calling on the administration, and the American government, to exert the strongest possible pressure on Egypt, including the threatening and enacting of sanctions if we have to," King said. "We have to take strong action. The time to look the other way is over."

Sen. Chris Murphy said that he was "hopeful that this administration is going to use the tools given to it by Congress to take a harder line."

"But if they do, I hope that it is a beginning of a much harder line taken. Not just in the context of our bilateral relationship with Egypt, but across the greater Middle East and across the world," the Connecticut Democrat said.

Just one day after Kassem's death, an Egyptian delegation -- including the Foreign Minister -- was in the Oval Office with Trump.

According to a readout from the White House, "Trump met with the foreign and water resources ministers of Egypt, Ethiopia, and Sudan to discuss progress on Grand Ethiopian Renaissance Dam talks."

"The President reaffirmed United States support for a cooperative, sustainable, and mutually beneficial agreement among the parties. The President emphasized that the United States wants to see all of these countries thrive and expressed hope that each country will take this opportunity to work together so that future generations may succeed and benefit from critical water resources," the readout of Tuesday's meeting from Deputy Press Secretary Judd Deere said.

The White House declined to comment when asked if Trump brought up Kassem's death to the Egyptian officials.