STATE COLLEGE — A Pennsylvania man remained jailed on Sunday after being accused by authorities of planning a mass school shooting for later this month that would have coincided with the anniversary of the Columbine High School massacre.

Police allege Braeden Phillips, 20, had planned to commit a mass shooting at State College High School on April 21, one day after the 26th anniversary of the deadly Columbine High School shooting, according to a criminal complaint.

Police allege Phillips had compiled a “hit list” and that the shooting would have taken place about 8:40 a.m. — a high traffic time for students and staff — near the school’s main staircase. Officials cited in the complaint allege that Phillips planned to place bombs in the school bathrooms.

Phillips has been charged with conspiracy to commit murder and unlawful possession of a firearm. He was being held without bond at the Centre County Correctional Facility because he was deemed an “extreme danger to the community,” according to court records.

Police were trying to determine if anyone else was involved in the plan. Authorities allege Phillips said a juvenile friend also was going to take part in the shooting.

Authorities were first alerted to the plot by staff members at a Centre County youth center, who told police a resident had shared information about it. Police interviewed Phillips’ friends and others, who told investigators that Phillips detailed how he planned to carry out the shooting and showed them a handgun.

When police asked if Phillips had any issues or grievances with State College High School, a friend said Phillips had told him, “the school did not serve his educational needs and failed him,” according to the complaint.