He was shot and killed in August 1922, during the Irish Civil War.
I have visited the area of Beal-na-mBlath, where Collins was shot and killed, on a couple of occasions while visiting County Cork.
Collins has become the poster boy for democratic political strategy for the Republic of Ireland. His short life and assassination has made him a revered hero that never had to face the test of time. The great tragedy of Collins' death is the potential that he could have achieved had he lived on.
Collins not only mounted an intelligence war against the British in Ireland but also simultaneously built a credible bond issue that raised vital cash and legitimacy for the Irish republican cause in the midst of a violent war of independence.
He was a courageous, intelligent martyr.
If you have not watched the 1996 film, Micheal Collins, consider renting it. While the movie is a romantic editorial and an over-indulgent sermon which plays up the tragedy of Collins' death and the bloody wars of independence and the civil war, I continue to love it. Perhaps even better than the movie is the "B" side of the DVD which features a balanced historical perspective full of videos, documentaries and interviews related to that bloody period of Irish History.
I named my middle guy, Liam Micheal Collins, after him.