African Americans were not the sole targets of crowd violence. One of the most brutal and well-documented events of the riot was the murder of Colonel Henry O'Brien, Commander of the Eleventh New York Volunteers. On Tuesday morning, O'Brien's regiment had come to the assistance of a detachment of policemen who were under attack at Thirty Fourth Street and Second Avenue. As the police battled rioters, O'Brien's men set up a six-pound Howitzer cannon in the street and fired above the heads of the crowd to frighten them off. Historical sources disagree over what happened next. The New York Tribune reported that two children were wounded by the cannon shots fired by O'Brien's men, one fatally; other reports claim that the shots killed seven, including a mother and her young child. What is clear is that the rioters remembered O'Brien's order to fire, and went looking for him that same afternoon.