Among their targets, the Church, they also wish to attack the Bourbon Monarchy as well.
All their majestic appearance is just the fruit of oppression and will be us the oppressed ones who will finish it through insurrectional revolutionary violence. We won't fall in the trap of awaiting for the historical conditions to come. We believe that the conditions for the attack are propitious as long as State, Capital and even more the rotten fascist Royal Family exist. We are determined. We do not wait. We take action.
We do not have the wrong idea that with just this kind of actions we will achieve the destruction of all that oppresses us. We do not deceive ourselves. We do not fall into self-complacency. This is propaganda through action, which has existed for more than a century among the seditious and conspirators against Power. It is an appeal to war without limits using all our imagination and energy to end with this rotten reality.
The bomb was hidden in a trash bag, and was found by the local priest in a confessional, who then evacuated the church and called the police. The bomb was made of 200 grams of gunpowder in a can of nails with an alarm clock, which they successfully deactivated.
Another interesting detail from a Spanish language blog writing in English is the following note:
Note: Mateo or Mateu Morral was a famous Catalan Anarchist who attempted to kill King Alfonso XII in 1906 with a bomb hidden in a bunch of flowers that he threw against the royal parade in Madrid, killing several but not the monarchs. A historical video can be watched here[es].