"We wanted to show that Demi is all grown up from her Disney days and is a really beautiful and powerful woman now," Shields tells Us Weekly. "When I showed her the images she was really excited and could not wait for us to post them so that her fans could see a different side to her."
Lovato -- who will perform at the Iquique Festival in Chile Saturday -- was so impressed with the shots that she's now using one as her Twitter avatar.
"When you meet Demi she can be a real force of nature, and this particular image of her smashing the glass really captures that," Shields explains. "She looks amazing and was really great to work with."
Tell Us: Are you surprised to see a more adult side of Demi Lovato?