The elder John Marr had been a Commissioner in Chancery in the Supreme and County Courts, much like a court-appointed trustee in later times, as well as a justice of the peace.

The local judges gave him the same appointments held by his father; Marr also served a two-year term as sheriff of Fauquier County.

[8] On Saturday, June 1, 1861,[10] a company of Union Army cavalry on a scouting mission entered the streets of Fairfax Court House after driving back one Confederate picket and taking another prisoner.

[8] Lieutenant Charles Henry Tompkins of the 2d U.S. Cavalry Regiment led the Union force of between 50 and 86 men[11] who separated into two groups as they rode through the village.

[13][14] After Marr fell, first appeared former and subsequent Virginia governor and later major general William "Extra Billy" Smith, who had just resigned his seat in the U.S. Congress.

Lt. Col. Ewell had received a shoulder wound as he emerged from the village's hotel as the Union force first rode through the streets so he was bleeding as he took charge of the infantry company in the field and redeployed 40 of them.

[15] Ewell soon went off to send for reinforcements and Smith redeployed the men again in the same general area but in a less exposed position about 100 yards forward.

[18] The Confederates fired additional volleys at the Federals as they tried to pass through town again on their way back to their base near Falls Church, Virginia.

[20] Governor Smith later reported that Marr had apparently been hit by a spent round ball because he had a large bruise above his heart but his skin had not been penetrated.

[27] A monument to Captain Marr was erected on June 1, 1904, near the entrance of the Historic Fairfax County Courthouse, which was moved October 2020 to the Stuart-Mosby Civil War Cavalry Museum in Centreville, VA.

The monument reads: "This stone marks the scene of the opening conflict of the war of 1861–1865, when John Q. Marr, captain of the Warrenton Rifles, who was the first soldier killed in action, fell 800 feet south, 46 degrees West of the spot.