The Pentagon announced earlier this week it would execute Hasan by firing squad, the first of its kind since the end of World War Two. Then on Thursday US Defence Secretary Pete Hegseth said the execution would be livestreamed for the public.
“People need to understand that there’s serious consequences for these types of things,” said Hegseth.
The BBC has asked the White House whether Trump supported the plans.
Speaking to reporters on Friday, Vance said: “I see these announcements. I don’t know that that’s actually going to happen.”
The vice-president said that Hasan was meant to treat soldiers for mental illness and other problems and “took them at their most vulnerable and gunned down these people where they lived”.
The announcement over the livestream plans has been met with criticism from both political parties.
Republican Senator John Curtis pointed to Rome’s history of a “bloody spectacle” corrupting people who watched them, warning that public executions erode civilisations “when it cultivates an appetite for executions as a form of entertainment”.
Curtis said that Hegseth’s plan “risks feeding that appetite” and urged him to reconsider.
“The victims deserve justice administered with solemnity. Broadcasting a death diminishes us and is not an effective deterrent,” he said.
Democratic Senator Chris Murphy told CNN that the idea was “disgusting” and reminiscent of executions carried out by the Islamic State group.
The US Conference of Catholic Bishops condemned the decision to publicly livestream Hasan’s execution, expressing “shock and great sorrow” in a statement.
The UN human rights office told AFP that livestreaming it would be “tantamount to a public execution and would breach the absolute prohibition of torture”.