Slain Japanese journalist's partner tells of grief at Syria killing

(CNN) -- Mika Yamamoto's first day in Syria would also be her last.

A veteran war reporter, Yamamoto had accepted an assignment to cover the increasing violence in the country last month, as she had in the past in Afghanistan, Iraq and the Balkans.

Kazutaka Sato was her partner both in and out of work -- they both worked for Japan Press, an independent television news provider. He was just meters from her when she was shot.

Sato had covered many war zones with Yamamoto and describes her passion for journalism.

"I think it was her firm belief that you can stop a war with journalism ... she would also turn her attention to children. I believe she wanted to tell the world how they are hurt, dead and bruised in their hearts."

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Sato says he is not coping well with her loss and the only way he can find peace is to learn exactly what happened to his common-law wife.

He says they were in the besieged city of Aleppo with the rebel Free Syrian Army when he saw 10 to 15 men walking towards them. "At first I thought it was the Free Syrian Army, and we were on the same side so I held up my camera and started shooting. It was then that it happened."

Sato describes seeing one man in an olive green helmet, which made him think they were from the Syrian Army, but there was no way to be certain. As he turned and ran, he heard gunshots, followed by an automatic weapon firing. "I thought I was going to be hit and that's when I was separated from Mika," he says.

For the next hour he tried to find her, believing she was fine. "At no point did I think that she had died," he says.

"I asked a rebel fighter where Mika was. He told me, 'She's at the hospital, go and see for yourself.' At that point I pretty much imagined what had happened to her... On the first floor of the hospital, in the lobby to the left on a stretcher, I saw a body wrapped in a sheet. And I knew then it was Mika."

Video of slain journalist's final hours

Sato believes Mika was targeted because she was a foreign journalist. He says one of the armed men had shouted, "There they are, the Japanese," but it is difficult to determine exactly what was said from the video that captured her final moments.

Sato watches that footage -- filmed by Yamamoto when she was hit by the bullet -- for the first time. "In the video she's alive," he says in a quiet voice. "I don't know how I'm going to deal with this, I can hear her voice."

He has asked the Syrian government through the embassy in Tokyo to look into her death but says he holds little hope for an answer.

"I need to know what happened to her," he says. "Mika was the best part of my professional and personal life. She was my right hand, my left hand, my everything. I have no idea what to do now she's no longer here."