"Abandon all hope, ye who enter here..."
Little is known about Nathan's early life. Attending the high school Justin Leu taught in, he bonded with his teacher, whom he later cited as being the only reason he ever graduated. When he graduated from the school, Justin gave him a first-edition copy of Inferno, the first part of Divine Comedy (a 14th-century epic poem), which detailed the journey of its protagonist Dante through Hell while guided by the Roman poet Virgil. In the book, Nathan took detailed notes about its passages. When he became a student at a Seattle college, Nathan proved extremely unpopular. As a result, he began planning a series of Inferno-based killings with Justin, who by that point was spiraling into a psychotic breakdown due to his past. Intending to end the crimes in a double suicide, Nathan acquired SEMTEX from an unknown source and used it to construct a homemade bomb in his dormitory, which he planned to use to kill himself, Justin, and presumably an unknown number of others. Like Justin, he was also slowly suffering from a psychotic break. A week prior to Justin's first murder, he posted a blog about killing people at his school using the nine circles of Hell.
In Burn, he is first seen returning to his dormitory room, drawing scornful looks from the students he passes. After closing the door, Nathan immediately retrieves a box from underneath his bed, opens it up, and unlocks a secret compartment containing the SEMTEX and several other supplies. He inserts a battery in a cellphone, which he apparently designed as the detonator, before looking at the explosives in admiration and smiling in satisfaction. Hotch and Morgan later arrive at the college after the BAU, investigating Justin's murders, found his blog. Nathan stumbles upon them just as they find his stash of SEMTEX, and he tries to flee, only to be tackled by Morgan, who arrests him as he begins chuckling maniacally. Taken to an interrogation room, he is questioned by Morgan and JJ, to whom he confesses to being the unsub, all the while intermittently, silently whispering, "Abandon all hope, ye who enter here." However, his lie is exposed when he claims he strangled his first victim, a woman, when in actuality, the victim (who was a male) was bound and asphyxiated with gas. When JJ tells him this, Nathan begins chanting, "Abandon all hope, ye who enter here." JJ then identifies him as Virgil, to which Nathan proclaims he is Dante. He isn't seen again in the episode, but it can be assumed that he was institutionalized, considering his current mental condition and his unhealthy obsession with Inferno.
- Nathan constructing a bomb out of SEMTEX in his college dormitory and intending to use it in his suicide, as well as his threats against his schoolmates, could be a reference to Randy Slade, who committed a suicide bombing at his school using a bomb made out of SEMTEX.