SPOKANE, Wash. >> Prosecutors today filed 51 new charges against a 15-year-old boy arrested in connection with the shootings of four students at his rural Washington state high school.

A judge also decided that a decision on whether Caleb Sharpe will be tried as an adult will not occur until next spring.

In juvenile court today, Spokane County Superior Court Judge Michael Price set an April 2, 2018, date for the week-long hearing.

Sharpe is charged with killing one classmate and wounding three others on the morning of Sept. 13 at Freeman High School near the tiny town of Rockford.

Sharpe has previously pleaded not guilty to one charge of first-degree murder and three counts of attempted first-degree murder.

Spokane County prosecutors today upgraded the murder charge to premeditated murder, according to court documents. He was also charged with 51 counts of assault, representing other students in the vicinity of the shootings, documents said.

Regarding whether he will be tried as an adult, Price said the case was too complex to have a so-called declination hearing within 14 days as required by law.

“We have good cause to extend it beyond 14 days,” Price said.

Defense attorney Bevan Maxey agreed with the long delay, even though his client will remain in custody all that time.

“I have all kinds of concern for him being in jail,” Maxey said. “This is a process that is going to take place. Everybody needs to be properly prepared.”

“We would prefer he be handled as a juvenile,” Maxey said. “That’s what he is; 15 years old.”

Family members of Sharpe and the victims filled the small courtroom. They did not speak with reporters after.

Sharpe made no comments in the courtroom.

Authorities said Sharpe brought a handgun and an assault rifle to school in a duffel bag he carried onto his high school bus.

He shot a 15-year-old classmate in the abdomen and face, killing him, court documents said.

The teen then walked down a hallway, firing at or into the ceiling and wounding three female students, authorities have said. Sharpe told police that he had been bullied by the boy who died but did not target him specifically.

Sharpe also had been meeting with a school counselor because of suicidal thoughts and left a suicide note at home for his parents before the shooting, officials have said.

Sharpe has been in custody since the shootings.

The Associated Press doesn’t typically name juvenile suspects but is doing so because of the severity of the accusations and because Sharpe’s name was released in public documents.