We have used the visible integral-field replicable unit spectrograph prototype ( VIRUS-P ) , a new integral field spectrograph , to study the spatially and spectrally resolved Lyman- \alpha emission line structure in the radio galaxy B2 0902+34 at z = 3.4 . We observe a halo of Lyman- \alpha emission with a velocity dispersion of \approx 250 km s ^ { -1 } extending to a radius of 50 kpc . A second feature is revealed in a spatially resolved region where the line profile shows blueshifted structure . This may be viewed as either HI absorption at \approx -450 km s ^ { -1 } or secondary emission at \approx -900 km s ^ { -1 } from the primary peak . B2 0902+34 is also the only high redshift radio galaxy with a detection of 21 cm absorption . Our new data , in combination with the 21 cm absorption , suggest two important and unexplained discrepancies . First , nowhere in the line profiles of the Lyman- \alpha halo is the 21 cm absorber population evident . Second , the 21 cm absorption redshift is higher than the Lyman- \alpha emission redshift . In an effort to explain these two traits , we have undertaken the first three dimensional Monte Carlo simulations of resonant scattering in radio galaxies . We have created a simple model with two photoionized cones embedded in a halo of neutral hydrogen . Lyman- \alpha photons propagate from these cones through the optically thick HI halo until reaching the virial radius . Though simple , the model produces the features in the Lyman- \alpha data and predicts the 21 cm properties . To reach agreement between this model and the data , global infall of the HI is strictly necessary . The amount of gas necessary to match the model and data is surprisingly high , \geq 10 ^ { 12 } M _ { \odot } , an order of magnitude larger than the stellar mass . The collapsing structure and large gas mass lead us to interpret B2 0902+34 as a protogiant elliptical galaxy . This interpretation is a falsifiable alternative to the presence of extended HI shells ejected through feedback events such as starburst superwinds . An understanding of these gas features and a classification of this system ’ s evolutionary state give unique observational evidence to the formation events in massive galaxies .