No, Diego Portales is not living person. This Chilean building has a lot of historic memory in it walls. Since democracy arrived in our lives, in 1998, this building had been used as the central base for counting votes and for announcing the official results of the vote. A branch is occupied by the Defence Ministry. Before that, in 1972, the president Salvador Allende declared it a Cultural Centre, and in 1973, after the coup, it became the base for the Pinochet administration. Jorge Pérez explains this and other details in his blog (ES) , that are necessary to understand the historic value of this building.
The official reason for the fire, is that the building's electrical system hasn’t had proper maintenance. The fire damaged 40% of the whole structure. About the maintenance issue, Jorge Sepúlveda posts in his blog (ES) “the institutionalism falls down because of bad maintenance” he explains about different historic events and personal experience that helps to understand why these things happen, and how they are reflected in culture.
Another view of the situation comes from Pitufa, a witness of the fire, she was with some friends in the neighbourhood and wrote that the smell made them walk to Diego Portales building. While they were on their way, Pitufa shot photos, which are available here.