ROSEBURG, Ore. (CBS/AP) — A timeline of the campus shooting Thursday at Umpqua Community College in Roseburg, Oregon, shows police arrived at the scene six minutes after the first 911 call and exchanged gunfire with the shooter two minutes later.

The timeline released Saturday also shows the suspect was down two minutes after the shootout.

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Douglas County Sheriff John Hanlin told reporters at a Saturday news conference that the gunman, Christopher Sean Harper-Mercer, killed himself as officers arrived.

A Roseburg police officer and an Oregon state trooper were the first to arrive at the scene.

Authorities are trying to determine a motive for the mass killing.

Conflicting reports have emerged about whether the gunman singled out Christians as his victims.

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Roseburg Shooting Victims

Photos of the nine people who were killed at Umpqua Community College. (via CBS)

Janet Willis, grandmother of wounded student Anastasia Boylan, said victims who identified themselves as Christian were shot in the head.

However, the mother of another wounded student said the gunman asked his victims if they were religious but did not specifically target them if they were Christians.

Stephanie Salas, mother of 18-year-old survivor Rand McGowan, said the shooter asked about religion to let his victims know they were about to “‘meet their maker.”‘

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