Cpl. Nathan Cirillo never saw the gunman approach the National War Memorial before he was shot at twice, says Canada's top Mountie.

RCMP Commissioner Bob Paulson released details of Wednesday's shooting in Ottawa, including that the shooter ran toward the Tomb of the Unknown Soldier from the west side, while Cirillo and fellow reservist Brandon Stevenson faced south.

Paulson said the shooter was at an angle where Cirillo would not have been able to see him, and fired twice at Cirillo. He also fired once at Stevenson, but missed.

Ron Foxcroft, the honorary colonel of the Argyll and Sutherland Highlanders of Canada regiment, said Brandon Stevenson briefly chased the shooter before returning to the war memorial to try to revive his wounded friend. Foxcroft said he showed "tremendous bravery" in pursuing the shooter, later identified as Michael Zehaf-Bibeau.

"The only thing I know is he tried to go after the shooter. That’s all I know, and I’ve been told that by several people,” Foxcroft said.

An image from a Facebook memorial page dedicated to slain Cpl. Nathan Cirillo, right, also shows Brandon Stevenson, who chased the gunman that fatally shot Cirillo at the National War Museum in Ottawa on Wednesday. (Facebook) “I think he just went a few yards, but the shooter had such a head start on him.”

Cirillo's cousin, Ephraim Cirillo, told CBC News in Hamilton the shooter approached the pair from behind and shot Cirillo in the back. He said he had spoken with Stevenson, a friend he went to Cardinal Newman High School with in Hamilton, on Wednesday.

Neither Stevenson nor Cirillo were armed when the attack took place. The rifles they carried as honour guards were not loaded.

Stevenson returned to Cirillo's side and tried, along with several bystanders, to revive the wounded reservist, Foxcroft said. Cirillo was transported to hospital where he died of his wounds.

The pair were both colleagues and friends, Foxcroft said. Several photos posted on a Facebook memorial page devoted to Cirillo show the two together, either in military clothing or out partying.

"They were very close. Obviously, [Stevenson] is in a state that we’d all be if we just lost our best friend," Foxcroft said, adding that the reservist is already getting grief counselling.

"We have people down there with him in Ottawa and we’re arranging to get him back to Hamilton."

Sisters overcome with grief

Outside the armoury, Hamilton Mayor Bob Bratina said the Argylls sent 68 soldiers to Afghanistan and they all came back, only to lose one on home soil while serving as an honour guard. He said he visited with the family Wednesday night and spoke with Cirillo's two older sisters.

"They were grief stricken to the point where we weren't able to converse at too great a length," Bratina said, adding that Cirillo's kindergarten-age son, Marcus, was wondering why his aunts were crying.