Living entities in a group communicate and transfer information to one another for a variety of reasons. It might be for foraging food, migration, or escaping from obstacles and threats that may appear suddenly. They do so by interacting with each other and also with the environment. Statistical mechanics and information theory can be useful to develop the tools to quantify and analyse the flow of information among the living entities. The living entities can be modelled as active (i.e. self-propelling) particles. Here we consider a group of active particles under confinement. First we will show that the self-organisation of the particles can crucially depend on whether the confinement is soft or hard. Then we quench the trap boundary from soft to hard instantaneously. Consequently the self-organised cluster of the active particles, which was stable when the boundary was soft, becomes unstable and undergoes extreme deformation after the quench to find another stable configuration suitable for the hard boundary. Finally we will quantify the information regarding the quench that flows throughout the individual particles of the deforming cluster and show that the flow spans the whole cluster, propagating ballistically.