He could not be reached for further comment.
Two sources familiar with the matter said they believed the onetime employee was fired because of a bad temper and violent outbursts at the office. The sources asked for anonymity because it involved personnel information.
The Attorney General's Office served search warrants Friday on Washington's district offices in Philadelphia and Roslyn, seeking evidence related to campaign activity, The Inquirer has reported. Agents were asking for computer hard drives, calendars, paper files, and any other documents related to fund-raising or her political campaigning.
The exact nature of the probe is not known. No other legislators' offices were searched last week.
Officials with the Attorney General's Office have repeatedly declined to say whether Washington was being investigated.
Its agents have questioned at least two former high-level employees of Washington's, according to a source familiar with the investigation. Among other information, agents wanted to know about an annual political fund-raiser Washington holds that coincides with her birthday, and whether employees in Washington's district offices were tasked with helping to organize the fund-raiser using taxpayer-funded resources and while on the legislative clock, the source said.
Washington was first elected to the legislature in 1993 and served 12 years in the state House before being elected to the Senate in 2005.
Her district includes northwestern Philadelphia and pockets of Montgomery County. She serves on four committees, including Aging and Youth, where she is the ranking Democrat.