We have used targeted ALMA observations of SCUBA-2 sources to detect 75 >4.5-σ 850 micron sources in 100 square arcminutes of the Chandra Deep Field-South, by far the highest density sample of faint 850 micron sources yet obtained. The observed region matches the deepest portion of the 7 Ms Chandra image, making it possible to probe low-luminosity AGN at very high redshifts. We find that most of the ALMA sources appear to be consistent with having both their X-ray and submm emission driven by star formation. Indeed, only 20% of the ALMA sources have intermediate X-ray luminosities (rest-frame 8–28 keV luminosities of 1042.5-1044 erg/s), and none has a high X-ray luminosity (>1044 erg/s). Conversely, we find extreme star formation rates (>300 solar masses per year) in some intermediate X-ray luminosity sources, but not in any high X-ray luminosity sources. I will discuss how our results seem to be consistent with gas clearing from the galaxies.