 On November 28, 1909, Robertson was badly burned in an accident at Celtic Park, in Queens, New York when a ladle of hot lead exploded in his face.Robertson was preparing to pour the molten lead for a shot which was to be used in the shot put by Martin Sheridan and John Flanagan at the annual field day of the Second Regiment of the Irish Volunteers.The shot was determined to be a few ounces under weight, so a hole was bored in it and the lead was poured inside to bring the weight to the required mark.