The gun that was used in the Michigan school shooting was purchased by the suspect’s father on Black Friday, according to authorities.
Police said the 15-year-old suspect used a 9mm Sig Sauer, which contained several rounds of ammunition when authorities recovered it.
The suspect’s father bought the gun on Nov. 26.
"When they took it from him, he had a loaded firearm and he was coming down the hall," Oakland County Sheriff Michael Bouchard said at a news conference Tuesday. "That, again, I believe interrupted what potentially could have been seven more victims."
It is unclear where the firearm was purchased, and the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives is assisting with the investigation.
Police said that the suspect fired at least 12 rounds and that they found two 15-round magazines. The suspect's father reportedly also purchased three magazines.
"There allegedly were three that were purchased and he had," the sheriff said. "The crime scene unit, our forensic lab, is on the scene obviously processing a huge crime scene. More than likely that third magazine will be found there."
The suspect has declined to speak with authorities following his arrest and his parents have hired an attorney.
"There is no conversation that’s going on and no cooperation at that level," Bouchard said.
Oakland County Prosecutor Karen D. McDonald said her office will "issue appropriate charges quickly."
The suspect's parents could also face charges, which Bouchard noted "will all be up to the prosecutor."
"Ultimately we’re going to present everything how it played out and whatever applicable thing — I presume they’ll charge," he said. "We certainly want it charged."
The suspect had posted a photo of the gun online in the lead up to the shooting, but Bouchard noted his office was not made aware of any credible threats days prior to the shooting.
"It’s my understanding that this was a recent weapon purchase, that he had been shooting with it and had posted pictures of a target and the weapon," he said of the suspect. "That’s all part of what’s been looked at. We’re going to do a deep dive on the social media and all the activities of this young man."
The shooting left four students dead and eight other students and a teacher injured. The students who died have been identified as 16-year-old Tate Myre, 14-year-old Hana St. Juliana, 17-year-old Madisyn Baldwin and 15-year-old Justin Shilling.
At least two of the injured students are in critical condition in the hospital.