Black Summer is an eight-issue limited series written by Warren Ellis with art from Juan Jose Ryp.
Set a handful of years after the devastating events of the World Trade Center attacks on September 11, 2001, a defunct group of superheroes called The Seven Guns find themselves caught between a rock and a hard place. One of their members, John Horus, has murdered the President of the United States in cold blood as an act of "stopping corruption", starting a witch hunt for the rest of the Seven Guns and bringing about nationwide catastrophe in its wake. Crippled former "Gun" Tom Noir and the crew must rush to stop John Horus from committing anymore crimes while also searching their own souls for whether John's actions are justified. Meanwhile, someone thought to be long dead resurfaces to cause grief for the group while they try to carry out their mission.
Black Summer is typically regarded as the first part in Avatar's and Warren Ellis' "Superhuman Trilogy" dealing with the creation of superheroes. The other two books include No Hero (which also featured art by Juan Jose Ryp) and Supergod (featuring art by Garrie Gastonny). In an interview before the release of the first issue of Supergod Warren Ellis said "Black Summer was about superhumans who were too human. No Hero was about superhumans who were inhuman. Supergod is about superhumans who are no longer human at all, but something else. The third leg of a thematic trilogy if you like." [link]
Collected in Black Summer.