In the Chandra Deep Field South 1Msec exposure we have found , at redshift 3.700 \pm 0.005 , the most distant Type 2 AGN ever detected .
It is the source with the hardest X-ray spectrum with redshift z > 3 .
The optical spectrum has no detected continuum emission to a 3 \sigma detection limit of \sim 3 \times 10 ^ { -19 } ergs/s/cm ^ { 2 } /Å and shows narrow lines of Ly \alpha , CIV , NV , HeII , OVI , [ OIII ] , and CIII ] .
Their FWHM line widths have a range of \sim 700 - 2300 km s ^ { -1 } with an average of approximately \sim 1500 km s ^ { -1 } .
The emitting gas is metal rich ( Z \simeq 2.5 - 3 Z _ { \odot } ) .

In the X-ray spectrum of 130 counts in the 0.5 - 7 keV band there is evidence for intrinsic absorption with N _ { H } \gtrsim 10 ^ { 24 } cm ^ { -2 } .
An iron K \alpha line with rest frame energy and equivalent width of \sim 6.4 keV and \sim 1 keV , respectively , in agreement with the obscuration scenario , is detected at a 2 \sigma level .
If confirmed by our forthcoming XMM observations this would be the highest redshift detection of FeK \alpha .
Depending on the assumed cosmology and the X-ray transfer model , the 2-10 keV rest frame luminosity corrected for absorption is \sim 10 ^ { 45 \pm 0.5 } ergs s ^ { -1 } , which makes our source a classic example of the long sought Type 2 QSOs .
From standard population synthesis models , these sources are expected to account for a relevant fraction of the black-hole-powered QSO distribution at high redshift .