Robert Mueller's secret weapon has Trump's team scared: MSNBC
FBI Director Robert Mueller testifies during a House Appropriations Committee hearing on the FBI Budget, on Capitol Hill on March 19, 2013 in Washington, D.C. (UPI/Kevin Dietsch via Creative Commons)

On Monday, MSNBC host Ari Melber revealed the one person who scares President Donald Trump and his team more than Robert Mueller.

A prosecutor on special counsel Mueller’s team, Andrew Weissmann, has several of Trump's legal team worried because of his "hardball" tactics.

Melber explained that he is known for being "effective" and "controversial."

Melber said that unlike most prosecutors, Weissmann is not afraid to go after family members.

He then played a clip of pundits like Sean Hannity calling Weissmann "a legal nightmare."

Watch the special report below: