The nation's top intelligence official, who became a controversial figure in the wake of the Edward Snowden revelations about mass surveillance, has said he's stepping down. This morning, Director of National Intelligence James Clapper told the House Select Committee on Intelligence that he submitted his resignation letter, "which felt pretty good."

Clapper's resignation was not unexpected, but it does leave a key role for the new Trump Administration to fill.

Further Reading Clapper: We should have disclosed NSA bulk data collection in 2001

Clapper had over 50 years of military and intelligence service. His office was created after the events of 9/11 to oversee 17 other intelligence agencies. Clapper had moved into the private sector, but he rejoined government service in September 2001. He became the fourth director of ODNI in 2010.

After the Snowden revelations of mass spying, Clapper became a controversial figure. In 2014, several members of Congress said Clapper should be fired, but President Barack Obama decided to keep him on.

The source of the controversy dated to 2013, before the Snowden leaks. Senator Ron Wyden asked Clapper directly: Did the NSA gather "any type of data at all on millions or hundreds of millions of Americans?" Clapper responded: "Not wittingly."

He later went on to explain that answer as the "least untruthful" response he could have given.

Earlier this year, Clapper was asked by key members of Congress for even a "rough estimate" of how many Americans are being spied on. He didn't provide one. "If such an estimate were easy to do—explainable without compromise—we would’ve done it a long time ago," he said.

"I will leave this job concerned about the impact of so-called lone wolves and home grown violent extremism," Clapper told the committee today. "That is a very complex problem."