President Obama went through with a campaign appearance in Las Vegas on Wednesday evening and, after laboring to quiet an exuberant crowd, began his speech with a somber tribute to the four Americans killed Tuesday in Libya.

Obama, visibly weary and seeming to struggle to display the usual energy and sharpness of his campaign appearances, opened with a description of the “tough day that we’ve had today.” With a crowd of more than 8,000 at a Las Vegas convention center still screaming and cheering, Obama, wearing no jacket and his sleeves rolled up, held up his hands and paid tribute to the dead, who he said “were working to advance the interests and the values that we hold dear as Americans.”