The Michigan school shooting suspect allegedly posted a picture of the semi-automatic handgun used in the massacre on social media before he opened fire on classmates and teachers at Oxford High School, according to the local sheriff.

“It’s my understanding, again, that this was a recent weapon purchase,” Oakland County Sheriff Michael Bouchard said Tuesday night about the 9mm Sig Sauer SP 2022 pistol the suspect’s father bought on Black Friday.

“He had been shooting with it and posted pictures of a target and the weapon. That’s all part of what’s being looked at. We’re going to do a deep dive on the social media and all the activities of this young man,” he added about the 15-year-old Oxford High School sophomore, CNN reported.

Local outlet Fox 2 Detroit also reported that before the suspect’s social media pages were taken offline, he posted what appeared to be a countdown.

“Now I become death – destroyer of worlds – see you tomorrow Oxford,” he reportedly wrote on Instagram, according to the outlet.

Authorities have not commented on that post but investigators insisted that they would scour the social media posts of the alleged shooter.

A motive for the shooting is still unclear.

The handgun used in the attack was purchased by the boy’s father on Black Friday, four days before the shooting, Bouchard said, adding that the dad allegedly bought a third magazine that law enforcement officers have not yet found.

He did not say where the gun was purchased and whether it was new or used.

The suspect had at least two 15-round magazines, including one with seven remaining bullets, when he was arrested, the sheriff said.

“When they took it from him, he had a loaded firearm. He was coming down the hall. That again, I believe, interrupted what potentially could have been seven more victims,” he added, according to the Detroit Free Press.

Several parents told the Free Press that their kids heard rumors of planned violence before school Tuesday — and some took it seriously enough to prevent their children from going to class.

However, Bouchard said that “none” of the rumors had been reported to the police. 

A search warrant was executed at the teen’s home and authorities retrieved several items, including the boy’s phone, he said.

Several apparent long guns also were removed from the home by Oakland County Sheriff’s Office investigators and FBI agents, Fox 2 Detroit reported.

Andy Arena, a former FBI special agent, told Fox 2 Detroit that “the next few days are going to be key to see what caused this individual to do this. Was this a random act, or was there a specific reason he went after these individuals — usually there is — usually in hindsight, they went after a (certain person).”

Arena added: “A lot of this is going to hinge on forensics, particularly what this individual was looking at on his computer, and what he was doing on social media. His activity on social media.”

Cyber forensics investigators will not only look at what the suspect posted, but what he deleted.

“What was he looking at? What was he searching? What was he reading?” Arena said. “Those type of things. It will give us a clearer picture to see what was in his mind and what drove him to do this horrific act.”

The accused shooter is being held at Children’s Village and is not cooperating with the police. His name has not been released pending criminal charges.