The alleged gunman at Oxford High School, Michigan, recorded a video of his murder plans the night before the crime, according to police. In the video, the 15-year-old talked about shooting students at his school the next day, said police officer Tim Willis from the Oakland sheriff's office on Wednesday at the first appearance of the accused at a magistrate. Judge Nancy Carniak ordered the suspect to be transferred from a youth facility to a county jail, where he would remain isolated from other inmates. The accused was connected via video.

Prosecutor Karen McDonald had previously announced that the 15-year-old suspect would be charged as an adult.

The tenth grader was accused of, among other things, terrorism resulting in death and fourfold first-degree murder, she said.

Under Michigan law, juveniles could be charged as adults in such particularly serious crimes.

"First degree murder is the worst of all these crimes."

Motive still unclear

After viewing evidence, she was sure that it was a deliberate act.

For procedural reasons, she could not comment on the details.

The prosecutor said she had promised the father of one of the victims "that I would treat this case as if it were my own children".

The shooter opened fire on Tuesday at Oxford High School north of the metropolis of Detroit. Four of his classmates, aged between 14 and 17, were killed. Six other students and a teacher were shot injured. The perpetrator was arrested. His motive is unclear. According to the police, he refused to testify.

Sheriff Mike Bouchard said Wednesday the police had no information about the suspect prior to the crime.

However, it was later learned that representatives of the school had been in contact with the student the day before and on the day of the crime, "because they considered his behavior in the classroom to be questionable".

The parents of the accused were still in the morning for a personal interview with school representatives in the high school.

"The content of this meeting is obviously part of the investigation."

Prosecution against parents not excluded

Bouchard said the shooter fired more than 30 shots on Tuesday. When he was arrested, he still had 18 unused cartridges with him. Police said they had confiscated a handgun belonging to the alleged perpetrator's father. It is still unclear how the perpetrator got hold of the weapon that was acquired just a few days ago. Bouchard said it could not be ruled out that charges could be brought against the parents.

Fatal incidents continue to occur in the United States because shooters open fire in schools.

That is why many schools have such crisis scenarios practiced on a regular basis to ensure that students are prepared in the event of an emergency.

Gun laws in the United States vary from state to state, but firearms such as pistols and assault rifles are usually relatively easy to come by.

Stricter gun laws usually fail because of the Republicans in Congress and the powerful gun lobby.

US President Joe Biden has announced measures to curb armed violence, but so far without concrete results.