On their way to the telegraph office, Colonel Ellsworth looked up toward the flag flying over the Marshall House, just as they passed it. "That flag must come down, Boys!" declaimed Ellsworth.
He sent a member of Company A back to the wharf to bring up a group of men as quickly as possible, with the idea in mind that they, not he, would remove the flag. Just as the soldier rounded the corner for the wharf, Ellsworth changed his mind.
He entered the Marshall House, removed the flag, and was shot dead for his efforts. Moments after the double shooting of Ellsworth and Jackson, Knox and his men arrived at the hotel. Quietly, Knox was informed of the situation.
I ascended the stairs. Stepping over the body of Jackson, who still lay where he had fallen, I entered the room where all that was mortal of my beloved friend and commander lay silent in death. I will not attempt to describe my emotions while gazing on that sad scene. I could scarcely credit my own senses. There lay one whom I had seen only a few minutes before, full of life and the vigor of early manhood, cut down without a moment's warning by the hand of the assassin. His face wore a very natural expression and, excepting its pallor, his countenance looked the same as in life.
Knox, as an officer of the Fire Zouaves, fought in the Battle of First Bull Run, charging the enemy, "with a wild, wild yell, three cheers, and a loud, fierce cry of 'Remember Ellsworth!.'"
After Bull Run, Edward Knox was among the officers who resigned after Ellsworth's death in order to return to New York and organize the 44th New York, known as the "People's Ellsworth Regiment," or "Ellsworth's Avengers."