After the shoe was completed, the artist invited the public to take pictures.
Explanation:
The reason behind this is that there are two arguments to find reason in the answer. First of all, the artist couldn't let the pubic interact with the work if it was unfinished. Therefore the had to wait until it was finished to allow them to react with it. Second, the picture shows us that the artist invited the public to take pictures of the work after it was completed because he uses body language in the picture to encourage them to approach to the work.
