Earlier on Thursday, a van crashed into dozens of people in Barcelona's city center. El Periodico newspaper citing police reported that the incident with the van which drove 530 meters hitting pedestrians was confirmed to be a terrorist attack. The Catalan Interior Minister later announced that the attack took lives of 13 people.
Twitter users started to post the pictures and gifs of cats and dogs with the hashtag #Barcelona. The tweets call on users not to panic and share the images of their pets instead of the pictures of the incident.
A similar flashmob was launched on Twitter follwing the Brussels terror attacks in March 2016.