The DPD are probably ostensibly doing an internal affairs investigation of their own, but Raleigh PD has a duty to the victim to conduct their own investigation.
Yes, I just found the headline misleading. The other news sources say that Raleigh PD is investigating the incident. I guess Chalmers decided he had better issue a press release saying they are looking into it. I wonder why the DPD guys didn't identify themselves as off-duty officers?