Cox was among the war party raised in the Cariboo during the Chilcotin War, riding west from Alexandria, British Columbia with 50 men raised in the goldfields to meet the corresponding party of the New Westminster Rifle Corps, mostly former Royal Engineers, led by Governor Seymour and Chief Constable Brew, who had disembarked from HMS Sutlej at Bella Coola and entered the Chilcotin District from the west.
and Helen B. Akrigg as "friendly, genial and easy-going", encamped at Puntzi Lake on June 12, 1864, four days after leaving Alexandria, and did not very much in advance of the arrival of Seymour's and Brew's contingent other than build minor fortifications.
Cox was discouraged at the death of McLean, who was a noted and self-touted "Indian killer", and wanted to abandon the pursuit but Governor Seymour insisted he persevere in the hunt, partly because given the expense of the expedition he had to have something to account for upon his return to the capital.
The Governor and his officials, however, had made no such promise and Klatassine and his men were arrested and eventually tried and hanged for murder at Qiesnellemouthe (today's Quesnel).
In 1868, Cox was among those who opposed an address to the Queen prepared by John Robson, Amor de Cosmos, Edward Stamp and G.A.B.