Patrick Shanahan, the deputy defense secretary, will succeed defense secretary James Mattis and serve as acting defense secretary at the Pentagon.

Before being appointed as Mattis' deputy in 2017, Shanahan worked as a Boeing executive for decades.

The Washington state native was known throughout Boeing as a problem-solving "Mr. Fix-It."

It's official — deputy defense secretary Patrick Shanahan will be taking the helm at the Pentagon as acting secretary of defense.

James Mattis, who resigned from the position over US President Donald Trump's decision to pull troops out of Syria, will be forced out of the role before 2019. In his resignation letter, Mattis had offered to stay on for two months in order to facilitate a smooth transition.

Read more: Trump is forcing out Defense secretary James Mattis by New Year's instead of allowing him to stay another 2 months

Instead, Trump announced his new pick in a tweet on Sunday. He praised Shanahan, writing: "Patrick has a long list of accomplishments while serving as Deputy, & previously Boeing. He will be great!"

But who exactly is Shanahan, and what sort of experience will the Washington state native and father of three bring to the role?

Here's a look back at Shanahan's life and career: