Some speculation, but please check me on the facts.
It looks like (google map) and sounds like (ATC recording) that 3407 was flying towards the ILS to intercept it. I thought I heard the ATC say something about no autoland, due to variances in the ILS. So where the plane went down (about 1-2 miles north of the runway 23 centerline), looks like it might be a spot where one might disconnect the autopilot, to hand fly the ILS capture and final descent.