Give some stream of consciousness and then the answer. The mass shooting occurred between 10: 05 and 10: 15 p.m. PDT on October 1, 2017, which was the third and final night of the festival. When the shooting began, country music singer Jason Aldean was giving the closing performance.

Based on this passage, who was playing during the las vegas shooting?
To answer the question, consider the following: When the shooting began, country music singer Jason Aldean was giving the closing performance.
Therefore, the answer is country music singer Jason Aldean.