Fitzsimons was killed in a German air raid on September 4, 1917 along with Pvt. Oscar Tugo, Pvt. Rudolph Rubino and Pvt. Leslie Woods, when bombs fell on Base Hospital No. 5 near Dannes-Camiers in Pas-de-Calais, France. In 1920, Army Hospital 21 in Aurora, Colorado was officially renamed the Fitzsimons Army Hospital in his honor.