Canadian and U.S. military officials announced here early this morning that the “initial findings” of a joint investigation warrant a further probe to determine precisely how the two died and the five – including three Canadians, an American and one Afghan – were wounded.
A news conference to give further details is scheduled for later today.
The casualties occurred in the late hours of last Tuesday or early Wednesday during a fierce firefight with the Taliban at a remote base in the southern province of Helmand.
The battle, which raged for hours, was originally precipitated by an ambush earlier on Tuesday upon an Afghan National Army convoy returning to Forward Operating Base Robinson, as the wide-open settlement in the Sangin River Valley is known.
Eight Afghans died in that first attack.
It was in support of that beleaguered convoy that a Quick Reaction Force -- composed of Pte. Costall and 37 other Canadians from the 7 Platoon, First Battalion of the Princess Patricia's Canadian Light Infantry -- was choppered to the remote base.
Some short time after the QRF arrived and darkness fell, the Taliban launched an all-out assault on the base itself.
The primitive base, which has no sanitary facilities and no permanent structures, is little more than an expanse of sand surrounded by a single ring of sandbags.
Some 10 metres beyond the sand berm lies a frail perimeter of concertina wire, and beyond that wire, various small hills and compounds from which the Taliban attacked the base in three directions.
It was at the north end of the camp, in the relatively narrow space between the sand berm and the wire, that Pte. Costall, who was laying down a protective fire base for his fellow soldiers as they rushed to repel the Taliban, was killed.
That gate is now named Costall Gate after the young married father of one.
From inside the sand bags, the coalition forces -- then manned by about 100 ANA soldiers, their U.S. trainers and the QRF -- would have been shooting outwards.
Over the weekend, hundreds of soldiers from the PPCLI made the arduous trek by Light Armoured Vehicle to reinforce the base, arriving just yesterday morning.
The investigation by the Canadian Forces National Investigation Service and the U.S. military will continue.
Asked how friendly fire might have been responsible, Maj.-Gen. (Ret.) Lewis MacKenzie told CTV News on Monday that investigators would start with the ammunition.
"The most obvious one is calibre of the bullets that stuck the soldiers," he said.
Even an examination of bullets might not provide the whole answer, however, because Afghan National soldiers are armed with AK-47 assault rifles, the same weapon favoured by the Taiban.
"There would also be the interrogation of our folks that were involved in the firefight," Gen. MacKenzie said.
He said investigators will try to recreate the battle, according to witness accounts, to figure out who was firing and why they were firing.
With a report from Canadian Press