Chief Robert F. Rufo Jr. said Donnelly handed in his letter of resignation, effective at 5 p.m.
Woburn police leaders had placed Donnelly on administrative leave last week and opened an internal affairs investigation into news reports that allegedly linked him to the planning of the Charlottesville, Va., rally where a woman died after a white nationalist drove his car into a crowd of protestors.
Behind-the-scenes video of the event allegedly showed Donnelly, who was then a reserve officer in Woburn, acting as security for Richard Spencer, a white nationalist leader, at a meet-up. Donnelly reportedly calls himself Johnny O'Malley when introducing himself.
Chief Rubo said the department's investigation would continue despite Donnelly's resignation.
"A thorough finding of fact is necessary in this situation, and our investigation shall continue," Chief Rufo said in a news release. "For decades, police chiefs across the commonwealth have called for a statewide certification process to ensure that allegations of misconduct are thoroughly investigated, and bad actors are held accountable. That will be our focus moving forward."
The Middlesex District Attorney Marian Ryan said last week that her office would review every case Donnelly worked on as the allegations against him "tear at the fabric of trust between communities and the police departments that serve them."
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