I am so sorry to hear about this occurrence. It is truly saddening and I pray for all of those that lot loved ones in the tragedy.
About the whole Mt. Vesuvius thing.. I would look into it and see if it really i due for another eruption. A good sign that it may erupt soon is if there are other earthquakes and tremors around its surrounding areas. If there is increased seismic activity around the volcano, then that is a great possibility. Other than that, however, it was probably a shift in the tectonic plates that lie under Italy. If that is the case, then there is no need to worry about the volcano at this present moment.