The Oakland County Sheriff now says a 15-year-old suspect fired more than 30 rounds in an attack at Oxford High School that killed at least four people and injured seven others.
Sheriff Michael Bouchard walked through the school Tuesday night, discussing his observations and other case details afterward in a Wednesday morning interview with CNN.
Authorities said Tuesday that three students were killed and eight others - seven students and a teacher - were wounded in the shooting. But Wednesday, Oakland County Undersheriff Mike McCabe confirmed a fourth student, 17-year-old Justin Shilling, died at 10 a.m. due to gunshot wounds sustained at the school.
"The evidence I've seen there shows he was very clearly trying to kill people," Bouchard said in the television interview.
"I've seen some of the actual video of the shooting itself. It's clear that he came out with the intent to kill people. He was shooting people at close range, often times toward the head or chest ... It's chilling. It's just absolutely cold-hearted, murderous."
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Bouchard said the suspect, who he did not name, is not speaking with law enforcement and his family has retained an attorney.
After additional review, Bouchard said, investigators now believe the suspect fired more than 30 rounds in the school. That's based on finding additional shell casings at the scene; on Tuesday, law enforcement said they thought there were 15 to 20 shots and the suspect had at least two, 15-round magazines for a 9mm Sig Sauer SP2022 pistol.
Law enforcement also found something written by the suspect that may point to motive, Bouchard said.
"We can't get the motive from the suspect that we have in custody, but we think we've for a path to get a lot of supportive information as to how and why this occurred," Bouchard said.
The sheriff also spoke about images contained in a viral video posted by a student in the school. The video appears to show someone pretending to be law enforcement in an effort to gain access to a classroom where students and staff were hiding.
"We know he tried to breach classroom doors, he actually fired through a number of the doors that I looked at last night, through the barricaded doors," Bouchard said.
On Tuesday, Bouchard said the suspect's father bought the gun on Black Friday. The prosecutors will review how the suspect obtained the weapon and whether that warrants criminal charges for the suspect's parents, the sheriff said.
More information is expected later this afternoon from prosecutors and law enforcement.
Contact Dave Boucher at email@example.com or 313-938-4591. Follow him on Twitter @Dave_Boucher1.
This article originally appeared on Detroit Free Press: Oxford High School shooting: Sheriff details surveillance video