A 15-year-old boy was charged Wednesday with murder, terrorism and other counts for a shooting that killed four fellow students and injured others at Michigan's Oxford High School.

Charges against Ethan Crumbley were announced Wednesday, a few hours after authorities reported the death of a fourth teen from the school in southeastern Michigan. Crumbley is charged as an adult with one count of terrorism causing death, four counts of first-degree murder and seven counts assault with intent to murder.

Prosecutor Karen McDonald did not reveal a possible motive for the shooting Tuesday at Oxford High School, located in a community of about 22,000 people roughly 30 miles (48 kilometers) north of Detroit. However, she said prosecutors are “confident” they can show the crime was premeditated.

“There is a mountain of digital evidence. Videotape, social media, all digital evidence possible," she said.

Deputies rushed to the school around lunch time and arrested the suspect in a hallway within minutes. He put his hands in the air as deputies approached, Oakland County Sheriff Michael Bouchard said late Tuesday at a news conference.

The boy's father on Friday bought the 9 mm Sig Sauer used in the shooting, Bouchard said. He did not know why the man bought the semi-automatic handgun, which his son had been posting pictures of and practicing shooting, Bouchard said.

The four students who were killed were identified as 16-year-old Tate Myre, 14-year-old Hana St. Juliana, 17-year-old Madisyn Baldwin and 17-year-old Justin Shilling, who died Wednesday.

Bouchard said Myre died in a patrol car as a deputy tried to get him to an emergency room.

A teacher who received a graze wound to the shoulder left the hospital, but seven students ranging in age from 14 to 17 remained hospitalized through the night with gunshot wounds, he said.

The gun the boy was carrying had seven more rounds of ammo in it when he surrendered, Bouchard said.

Undersheriff Mike McCabe said the student’s parents advised their son not to talk to investigators. Police must seek permission from a juvenile’s parents or guardian to speak with them, he added.

After the attack, authorities learned of social media posts about threats of a shooting at the roughly 1,700-student school. The sheriff stressed how crucial it is for such tips to be sent to authorities, while also cautioning against spreading social media rumors before a full investigation.

McCabe downplayed the significance of a situation in early November when a deer's head was thrown off the school roof, which he said was “absolutely unrelated” to the shooting. The incident prompted school administrators to post two letters to parents on the school’s website, saying they were responding to rumors of a threat against the school but had found none.

Bouchard said the student in custody in the shooting had no previous run-ins with his department, and he was not aware of any disciplinary history at school.

"That’s part of our investigation to determine what happened prior to this event and if some signs were missed, how were they missed and why,” he said.

The district said in a statement that all schools would be closed for the rest of the week.

Isabel Flores, a 15-year-old ninth grader, told Detroit television station WJBK that she and other students heard gunshots and saw another student bleeding from the face. They then ran from the area through the rear of the school, she said.

A concerned parent, Robin Redding, said her son, 12th-grader Treshan Bryant, stayed home Tuesday after hearing threats of a possible shooting.

“This couldn’t be just random,” she said.

Bryant said he had heard vague threats “for a long time now” about plans for a shooting.

At a vigil Tuesday night at LakePoint Community Church, Leeann Dersa choked back tears as she hugged friends and neighbors. Dersa has lived nearly all of her 73 years in Oxford. Her grandchildren attended the high school.

“Scared us all something terrible. It's awful,” Dersa said of the shooting.

Pastor Jesse Holt said news of the shooting flooded in to him and his wife, including texts from some of the 20 to 25 students who are among the 400-member congregation.

“Some were very scared, hiding under their desks and texting us, ‘We’re safe, we’re OK. We heard gunshots, but we’re OK.’ They were trying to calm us, at least that’s how it felt,” he said.