Fermi Gamma ray Space Telescope observations of the flat spectrum radio quasar 3C 454.3 show a spectral-index change \Delta \Gamma \cong 1.2 \pm 0.3 at break energy E _ { br } \approx 2.4 \pm 0.3 GeV .
Such a sharp break is inconsistent with a cooling electron distribution and is poorly fit with a synchrotron self-Compton model .
We show that a combination of two components , namely the Compton-scattered disk and broad-line region ( BLR ) radiations , explains this spectral break and gives a good fit to the quasi-simultaneous radio , optical/UV , X-ray , and \gamma -ray spectral energy distribution observed in 2008 August .
A sharp break can be produced independent of the emitting region ’ s distance from the central black hole if the BLR has a gradient in density \propto R ^ { -2 } , consistent with a wind model for the BLR .