Some very important lines:

He said Mr. Cosko was “caught in the act” of breaking into the office of Sen. Maggie Hassan, a New Hampshire Democrat for whom he had worked until being ousted earlier this year. Mr. Ahn said Mr. Cosko had served as a tech staffer with administrative rights in Ms. Hassan’s office, suggesting he had access to more sensitive information. And he had a graduate degree in information technology.
And this:
Mr. Cosko had been working for Rep. Sheila Jackson Lee, Texas Democrat, at the time of the doxing, and the government says he used his official login for at least one of his leaks of information.

Ms. Jackson Lee’s office has not responded to multiple inquiries from The Washington Times, though her staff has told Texas newspapers she has fired Mr. Cosko.
Sure.  After he got caught.

And if you think who he was working for had nothing to do with his actions...