The Langley, B.C., native was in the mall Saturday, just hours after his team played an afternoon game against the Boston Red Sox, when shots rang out in the mall's newly renovated food court.
Lawrie tweeted: "Pretty sure someone just let off a round bullets in eaton center mall .. Wow just sprinted out of the mall ... Through traffic ..."
He then described a chaotic scene in his next tweet.
"People sprinting up the stairs right from where we just were ... Wow wow wow."
Lawrie, who has over 125,000 followers, has been credited by some media with breaking the story.
Police have confirmed one person killed in the shooting and seven others injured.
Of the surviving seven victims, police say two were in critical condition and one had life-threatening injuries.
After Lawrie evacuated the mall, he snapped a photo of the outside doors and tweeted: "Rattled right now."