Former Vice President Joe Biden Joe BidenFormer Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick Bloomberg rolls out M ad buy to boost Biden in Florida MORE, a leading 2020 White House hopeful, said on Monday that ISIS leader Abu Bakr al-Baghdadi was killed in a U.S. military operation despite President Trump Donald John TrumpFederal prosecutor speaks out, says Barr 'has brought shame' on Justice Dept. Former Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick MORE's "ineptitude" as commander in chief.

"I’m glad President Trump ordered the mission," Biden said in a statement. "But as more details of the raid emerge, it’s clear that this victory was not due to Donald Trump’s leadership. It happened despite his ineptitude as commander-in-chief."

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The Democratic presidential front-runner also slammed Trump's "erratic behavior," saying to the president's decision to withdraw U.S. troops from northern Syria likely rushed the mission to take out the ISIS chief.

"His erratic behavior made it harder and more dangerous for the special forces carrying it out. And they had to fly through territory that is now hostile to the U.S., taking fire along the way—including territory we controlled just weeks ago," Biden said.

Trump was met with criticism earlier this month after he withdrew U.S. forces from northern Syria ahead of a Turkish assault on the area. The U.S. military previously leaned on the Syrian Democratic Forces (SDF), which is led by the Kurds, as the local ground force fighting ISIS. Ankara, however, considers the SDF to be terrorists.

The president announced al-Baghdadi's death early Sunday, saying U.S. forces cornered him in a tunnel.

The terror group's leader detonated a suicide vest, killing himself and three of his children, according to Trump. The president said he died while “whimpering and screaming."

Trump said on Monday that he is considering releasing parts of the video showing the raid.