Van Arsdale had served with Lafayette during the Revolutionary War and had met with him on August 16, 1824, the day after Riker's birth.

Van Arsdale and the Veteran Corp of Artillery, of which he was a member, had received Gen. Lafayette at the Battery, on that day.

He began the practice of law, but stopped shortly after the Civil War erupted and he answered President Abraham Lincoln's call to arms to put down the rebellion.

In early 1862 Riker was courtmartialled for creating a false roster, for extorting money from sutlers and for keeping a woman in his headquarters.

Riker was killed in action at the head of his regiment on the right wing of the Federal line at the Battle of Fair Oaks on May 31, 1862.

At a meeting of the friends of Colonel Riker held on June 7, 1862, at the Everett House, New York, which was attended by, amongst others, George W. Morton, Ex-recorder Frederick A. Tallmadge, Mr. E. B.

Bradley gave a long and interesting account of the part played by the regiment in the battle of Fair Oaks from which Riker's coolness under the most trying situations was evident.

Riker's body lay in state at the Governor's Room of New York's City Hall and on June 10 his body, along with that of Colonel James Miller of the 81st Pennsylvania who had been killed in the same battle, was escorted by the New York State Militia (specifically the Fifth Regiment, a battalion of the Fifty-fifth Regiment, a troop of horse, a troop of Lancers and the Harlem Chasseurs), to Green-wood Cemetery, Brooklyn, where Riker's body was placed in a temporary vault while it awaited permanent interment.