Colonel James P. McMahon took command of the 164th New York Volunteer Infantry in 1863 after his brother, Colonel John E. McMahon, had died of disease that March. James led the regiment until his death in the battle of Cold Harbor on June 3, 1864. Early that morning, the 164th was ordered forward against the entrenched Confederate Third Corps. The Army and Navy Journal reported on his death: “Leading his men to assault the enemy’s works he daringly dashed ahead, and foremost, fighting with the National colors in one hand, was in the act of planting them upon the earthworks which entrenched the foe, when his body was pierced with six bullets by the Rebel sharpshooters.”
Bio of him here: http://albany.nygenweb.net/bio-42.htm
Find A Grave memorial: https://www.findagrave.com/memorial/70003794/james-p-mcmahon
More on the 164th New York: http://www.acsu.buffalo.edu/~dbertuca/155/164thNYVols.html
James P. McMahon
Captain, 69th NY Co. K (Irish Brigade)
Lt. Col., 155th NYSV
Colonel, 164th NYSV (in this picture)
Killed June 3, 1864, Cold Harbor VA