In 1922 at Béal na Bláth in Co Cork, a convoy carrying Michael Collins, commander of the national army was ambushed by anti-treaty forces.
From the Wikipedia page:
On 22 August 1922, during the Irish Civil War, Michael Collins, Chairman of the Provisional Government and Commander-in-chief of the National Army, was killed in an ambush here by the Ryan Agents of Holycross anti-treaty IRA forces while travelling in convoy from Bandon. The ambush was planned in a farmhouse in Béal na Bláth close to The Diamond Bar. Commemorations are held on the nearest Sunday to the anniversary of his death. A memorial cross (coordinates 51.81356°N 8.85651°W) stands at the site of the shooting on a local road 1 km south of the village which was a dirt road when Collins was shot. A small white cross marks the spot where he fell.
You can read more about his final journey here where I found the b/w photo of the officers at the the site.
The colourised photo was posted on Facebook a few days ago.