A 15-year-old boy was charged with murder and terrorism for a shooting that killed four fellow students and injured more at a Michigan high school, authorities said Wednesday as they revealed additional details, including a meeting between troubled officials and his parents just a few hours before the bloodshed.

No motive was offered by Oakland County authorities, a day after violence at Oxford High School, roughly 30 miles (50 kilometers) north of Detroit. But prosecutor Karen McDonald said the shooting was premeditated, based on a “mountain of digital evidence” against Ethan Crumbley.

“This was not just an impulsive act,” McDonald said.

Indeed, sheriff’s Lt. Tim Willis told a judge that Crumbley recorded a video the night before the violence in which he discussed killing students.

Crumbley was charged as an adult with two dozen crimes, including murder, attempted murder and terrorism causing death. During his arraignment, he replied, “Yes, I do,” when asked if he understood the charges. Defense attorney Scott Kozak entered a plea of not guilty.

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“He deliberately brought the handgun that day with the intent to murder as many students as he could,” assistant prosecutor Marc Keast said in successfully arguing for no bail for Crumbley and a transfer to jail from a juvenile facility.

Earlier, Sheriff Mike Bouchard told reporters that Crumbley’s parents were called to the school Tuesday “for behavior in the classroom that was concerning.” The teen remained in school, and the shooting occurred a few hours later.

Bouchard didn’t disclose what had worried school officials. He said investigators believe the gun was already in school.

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“There is nothing that he could have faced that would warrant senseless, absolutely brutal violence on other kids,” the sheriff said, noting that Crumbley had an additional 18 rounds of ammunition when he was arrested.

In court, Keast said Crumbley entered a bathroom with a backpack and came out with a semi-automatic handgun, firing at students while moving down the hallway. The four students who were killed were 16-year-old Tate Myre, 14-year-old Hana St. Juliana, 17-year-old Madisyn Baldwin and 17-year-old Justin Shilling.

Deputies rushed to the school around lunchtime Tuesday and captured Crumbley within minutes of the shooting. His father bought the 9 mm Sig Sauer gun last week, according to the sheriff.

It was the deadliest school shooting since the Santa Fe, Texas, High School massacre in 2018, according to The Associated Press/USA TODAY/Northeastern University Mass Killings database. The U.S. has had 31 mass killings this year of which 28 involved firearms.

McDonald said charges were being considered against Crumbley’s parents.

“Owning a gun means securing it properly and locking it and keeping the ammunition separate,” she said.

The shooting should be a wake-up call for new gun laws in a country that has become “desensitized to school shootings,” McDonald told reporters.

“We have to do better,” the prosecutor said without offering specific changes. “How many times does this have to happen? How many times?”

She also said the terrorism charge fits.

“What about all the children who ran, screaming, hiding under desks? ... Those are victims, too, and so are their families and so is the community,” McDonald said.

Video posted on social media showed students rushing to get out of first-floor classroom windows rather than open a door to someone who claimed to be a police officer. Bouchard said he likely was a detective.

After the attack, authorities learned of social media posts about threats of a shooting at the 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.

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.

After the 2016 presidential election, Crumbley’s mother wrote an open letter to Donald Trump as a blog post. It suggested school trouble, financial struggles, resentments — but also hope for the future.

Jennifer Crumbley said she was skipping car insurance payments to hire a tutor to help her son, who was 10 at the time. She blamed the “common core” curriculum used by teachers.

“My son struggles daily, and my teachers tell me they hate teaching it but they have to,” Jennifer Crumbley wrote.

She also celebrated her right to own a gun, referring to her job as a real estate agent.

“As a female and a Realtor, thank you for allowing my right to bear arms. Allowing me to be protected if I show a home to someone with bad intentions,” she wrote. “Thank you for respecting that Amendment.”