Police report that a teenager in the US, accused of plotting a mass shooting, has been apprehended after distributing a narrative he authored detailing the intended assault.

Alex Ye, 18, was taken into custody in Maryland following a joint investigation by the FBI and Montgomery County police.

According to investigators, the high school student penned a 129-page "memoir" outlining his aspirations for notoriety through an attack on a school.

He shared the manuscript with another individual, who then alerted authorities.

"In the narrative, [Mr] Ye elaborates on planning a school shooting and devises strategies for its execution," police stated in legal documents.

The informant who brought the alleged attack plans to light had received a portion of the narrative via Instagram from Mr. Ye. The two had previously crossed paths at a psychiatric facility.

The informant informed law enforcement of "significant parallels between the protagonist" and Mr. Ye. The narrative revolves around a character who identifies as transgender and faces bullying in school, officials noted, suggesting that certain elements were drawn from Mr. Ye's personal experiences rather than fictionalized.

Authorities characterized the narrative, described as a "manifesto," as evidence of his contemplation to carry out an assault on an elementary school using a semi-automatic assault rifle.

Investigators also obtained handwritten drawings of violent shooting scenes, and online chat logs in which he threatens mass violence. Ye is charged with threats of mass violence.

Mr Ye, who was born female as Andrea Ye but now uses male pronouns, previously was hospitalized for one month in 2022 for threatening to "shoot up school".

As a result of the probe, police increased security at local public schools, although they said he had not attended his high school in several years and had been studying online.

Noted