Born in Corofin, Ireland, Brew served in the Royal Irish Constabulary where he ascended to the position of inspector. In 1858 he was recommended for the office of Chief Inspector of Police for the new Colony of British Columbia to maintain law and order in the goldfields. When he arrived in the Interior, however, he was appointed Chief Gold Commissioner as a constabulary was not established until after the Chilcotin War.
After the attack on the road crew which launched that war, Governor Seymour dispatched Brew to lead an expedition into the Chilcotin District from the head of Bute Inlet, which met up at Puntzi Lake with another expedition from the Cariboo led by William G. Cox to lead another from the Cariboo goldfields towns. The result of the expeditions was more a denouement than a show of force, with the two expeditionary forces camped out without any visible adversary, while the hunt for the Chilcotin warriors went on in the deep bush, resulting in the death by ambush of Donald MacLean, former chief trader at Fort Kamloops. The Chilcotin war leader Klattasine was persuaded to surrender on terms of amnesty, then summarily arrested and eventually tried and hanged for murder, along with five other Chilcotins, including Tellot, another of the rebellion's leaders.
Brew was well respected by his superiors and served numerous functions in the colony over the years: magistrate, acting treasurer, acting chief commissioner of lands and works, and appointed member of the Legislative Council of British Columbia He died in the Cariboo of acute rheumatism in 1869.
His epitaph was written by his friend Judge Begbie: “A man imperturbable in courage and temper, endowed with a great and varied administrative capacity, a most ready wit, a most pure integrity and a most humane heart.”
Brew's name was conferred on two mountain summits in British Columbia, both named Mount Brew. The higher one at 2891m is located just south of the Fraser Canyon town of Lillooet, and which is the second-highest in the Lillooet Ranges after Skihist Mountain. The other is just east of Likely, British Columbia in the Cariboo district, 2057m, adjacent to Quesnel Lake.