Some prominent U.S. legislators are calling on the White House to send the Uzbek man accused of killing eight people in a New York truck attack to the U.S. military prison in Guantanamo Bay, Cuba.

President Donald Trump said on November 1 that he is considering doing so, which would require him first to designate the man, Sayfullo Saipov, as an “enemy combatant.”

“I would certainly consider that. Send him to Gitmo,” Trump said. Trump tweeted later that he also believes Saipov “should get the death penalty” for saying he was “happy” after the attack and expressing allegiance to the Islamic State extremist group.

The military prison at the U.S. naval base in Cuba in the past has been used primarily to imprison militants captured by U.S. forces on the battlefield in Afghanistan and Iraq.

Trump’s predecessor Barack Obama deplored the practice, which he and other critics say denies basic legal rights to the prisoners, and sought to shut down the prison.

No detainee has been sent to Guantanamo since 2008. Moreover, Saipov is a legal U.S. resident who has a “green card” and normally would be entitled to the legal rights available to him under the U.S. civilian justice system.

But Senate Armed Services Committee Chairman John McCain was among those in Congress calling on Trump to send Saipov to Guantanamo.

“We must not consider these attacks on our homeland in isolation, but rather recognize them for what they are: acts of war,” McCain said.

“As soon as possible, the administration should notify Congress how it plans to proceed with the interrogation and trial of this suspect.”

Republican Senator Lindsey Graham also called on Trump to designate Saipov as an “enemy combatant,” contending that he needs to be more thoroughly interrogated to determine whether he was, in fact, acting alone, as New York authorities have said.

“It’s ridiculous to believe that one day of interviews in a hospital tells us all we need to know about Saipov’s terrorist ties,” Graham said.

Saipov has already been charged with terrorism under regular U.S. judicial procedures in a U.S. district court in Manhattan.

Prosecutors in presenting their case against him on November 1 said he waived his constitutional protection against self-incrimination and confessed to committing the attack in statements to FBI investigators.

Acting U.S. Attorney Joon Kim said there was nothing about charging Saipov in civilian court that would prevent him from later being declared an enemy combatant, however.

“That is a determination that will be made elsewhere,” he told reporters in New York.

White House Press Secretary Sarah Sanders said Trump, who called Saipov “an animal,” already considers the suspect to be an “enemy combatant,” though he has not as yet officially designated him as such.

“I think the actions he took certainly justify that,” she said.