Last night, Roger Waters brought his massive Us + Them tour to Brooklyn’s Barclays Center for the first of two nights at the venue, introducing new tour mate Bo Koster of My Morning Jacket and nodding to the anniversary of the 9/11 attacks on New York in the process.

As JamBase reports, Koster joins Waters touring band on keys after regular keyboardist Drew Erickson was injured. MMJ have previously backed up Waters on multiple occasions, including at 2012’s “Love For Levon” concert for Levon Helm, at 2015’s Newport Folk Festival and at last year’s Bridge School Benefit. No word yet on how long Koster will be with Waters and company.

Near the beginning of last night’s encore, Waters addressed the crowd and honored those lost in the September 11, 2001, attacks and those that were affected in the years since, saying, “This is a very sad anniversary for a lot of people in this town and we feel for the families of all the innocent people who were killed that day 16 years ago. And also for the first responders who died since from the diseases they got from working. And also the hundreds of thousands, even millions of people in the rest of the world who’ve died since that day because of what happened and our responses to it. So let our hearts be with all the innocent people all around the world whoever they might be, whatever their ethnicity or their color or religion.”

Waters returns to the Barclays Center stage tonight for round two. See his full schedule here.