As a regular tourist to Alexandria, I have often watched the DCA traffic and the helos transiting along the Potomac shoreline north of the Wilson Bridge on Route 4. In this tragic instance, the Blackhawk [PAT25} not only seems to be higher than the published procedure but also further west [ie over the river]. And according to that radar plot [post 80] , in the last moments it seems to rurn right [ie further west] exacerbating the situation.
MPN11, former Mil ATCO