On 3 June, Lieutenant Chris Marwood's Reconnaissance Troop of 42 CDO on Mount Wall, accompanying the 3 Commando Brigade Forward Air Control team commanded by Flight Lieutenant Dennis Marshall-Hasdell, encountered two rifle sections from the 4th "Monte Caseros" Regiment (Second Lieutenant Lautaro Jiménez Corbalán's 3rd Platoon of B Company from Mount Harriet).The night before, the section under Corporal Elvio Alberto Balcaza had detected the presence of British troops on Wall, and the section under Corporal Nicolas Víctor Odorcic moved forward to assist under the cover of the early morning mist.However, at around 11.00 hours (local time) the Recce Troop opened fire and two conscripts (Privates Celso Paez and Roberto Ledesma) were instantly killed, and their NCO (Odorcic) went down, concussed when shot in the helmet by one of the Marine snipers.