The military is investigating an accident that left one reservist soldier dead and four others seriously injured at CFB Petawawa.

A 5,000-pound truck carrying 10 reservists rolled over during a training exercise at about 10:30 a.m. Saturday, killing gunner Arielle Keyes-Oliver, 19, a Carleton University student.

She was a member of 30th Field Regiment, Royal Canadian Artillery -- a reserve unit based in Ottawa that returned to their headquarters this weekend with heavy hearts.

"We're going to have to find out what happened and make the training safer in the future if indeed it was a preventable accident," said Col. Paul Scagnetti, calling Keyes-Oliver a dedicated and vibrant young woman.

CFB Petawawa's base commander, Lt. Col. William Moore, said three of the injured soldiers are being treated in an Ottawa hospital, and the fourth in nearby Pembroke.

Moore said "they are in stable condition, and things are looking well."

The injured soldiers were identified as 2nd-Lt. Ryan MacIntyre, Bombardier Jordan Anstey, Bombardier Frederic Koch and Bombardier Alexander Mullaly.

Moore says reservists frequently train on the weekend, adding Petawawa is the closest large training centre for Ottawa-based reservists.

Keyes-Oliver came to Ottawa to study public affairs at Carleton University. She had been in the military for a year and a half, mostly with the 11th Field Regiment in Guelph. She transferred to the 30th field Regiment in Ottawa just six weeks ago.

Her family issued a statement through the Department of National Defence, thanking friends for their support in their time of mourning.

Her family said she was proud to be Canadian and proud to be in uniform. The statement also said Keyes-Oliver was a natural leader and concerned with everyone she came in contact with.

Defence Minister Peter MacKay also issued a statement saying he was `deeply saddened' by the loss.

The military has arranged for grief counsellors.

In Guelph, her friends are clinging to photographs and memories, remembering Keyes-Oliver as a natural leader who loved kickboxing and horseback riding, and could play the piano, drums and trumpet.

With reports from CTV Ottawa's Jonathan Rotondo and The Canadian Press