We study the topic of quantum entanglement in the extreme spacetime background of a black hole. It was suggested by Almheiri et al (AMPS) that, unlike what is commonly believed, the event horizon of a black hole past Page time is very disruptive and violent. This disruption at the event horizon manifests itself as the so-called rewall', which incinerates any infalling object. As a result, quantum entanglement across the event horizon is also broken, and this saves us from the information loss conundrum. AMPS did not propose a mechanism for suchfi rewall', and many have been speculating how to realize such a singular structure. In this thesis, following Brown and Louko, we study further the mechanism of singular energy density in the context of Minkowski spacetime. We generalize their one-dimensional model to three dimensions. We study two spherically symmetric generalizations of Brown and Louko's model. The rst is the creation of a null energy pulse with a time-dependent boundary condition at the space origin, and the second is the creation of an outgoing and an ingoing energy pulse by a time-dependent boundary condition at a nite radius r = a. Both models generate singular energy pulses which at first sight seems to be strong enough to break quantum correlations. However, a singular energy pulse is not enough evidence to show that quantum correlation is broken1. A divergent response of an Unruh-DeWitt detector is needed. Our calculation shows that the three dimensional spherically symmetric model with a time-dependent boundary condition at the origin can be singular enough to destroy the quantum correlations. A similar calculation shows that the spherically symmetric model with a time-dependent boundary condition at nite radius r = a is not singular enough, because the Unruh-DeWitt detector response does not diverge. Our contributions to this topic consist of two models; 3+1 D pointlike source creation and 3+1 D shell creation. In both cases, we extended Brown and Louko's 1+1 D model and studied properties of the energy density and response function.