We study the energy build-up and trigger processes responsible for a X1.2 class solar flare that occurred in NOAA AR 11748, having βγδ magnetic complexity observed on May15, 2013. The flare was well observed by ground based (Hα ARIES, Nainital) and space borne (SDO, HMI). The flare shows two ribbons structures. Morphology of the flare ribbons shows that the brightening propagates along the southern ribbon. We have noticed several Hα kernels that shows different spatially and temporally evolutionary behavior. On the contrary, we do not find filament associated with this event. Therefore, to explore the driver of instability leading to this highly energetic flare, we study the morphological evolution of the active region using SDO and Hα data. We also study the evolution of photospheric magnetic field parameters from SDO/HMI magnetograms in conjunction to the E/UV emission. From AIA EUV images, we note sets of coronal loops over the active region, which show upward motion with the time. We explicitly note mass ejection and disruption of coronal loops. From this study, we infer that this flare occurred in the lower corona as the coronal loops moved upward which gives the signature of magnetic reconnection beneath the uprising loops.