On March 5, the odor from the abandoned truck finally brought police to it.
The case that began with Matthew's worried family had now become one of the most disturbing multi-state homicide investigations in the region.
Why Michael Dabkowski Was Killed
After leaving New Mexico, Lannon went to New Jersey and confronted Michael Dabkowski.
Lannon told investigators Dabkowski had abused him in childhood and possessed photographs connected to that abuse. He said he demanded the photographs and killed Dabkowski after a confrontation.
The legal outcome does not depend on whether Lannon's allegation about the past was true. In October 2022, he pleaded guilty to first-degree murder for Dabkowski's death.
On December 21, 2022, he was sentenced to 35 years in New Jersey state prison. The sentence requires decades of imprisonment before parole eligibility.
That conviction gave prosecutors a final judgment in one murder while the New Mexico cases continued toward their own resolution.
The Claim of Eleven More Victims
During the early court proceedings, prosecutors disclosed another startling statement attributed to Lannon.
He claimed he had killed 11 additional people in New Mexico, mostly people he associated with the drug trade. Combined with the five known murders, that would mean 16 victims.
He described some alleged victims as having been shot and others stabbed. He also claimed bodies had been left in remote areas.
Police did not simply accept the claim. Authorities in New Mexico and New Jersey examined it and searched for corroboration.
They did not find it.
No additional bodies were publicly tied to the supposed 11 killings. No additional homicide charges were brought based on those claims. For that reason, Lannon can accurately be described as a man convicted of five murders who claimed a much larger number. It would be inaccurate to present the other 11 as confirmed victims.
Daniel Lemos
One of the people repeatedly drawn into the investigation was Daniel Lemos.
Early reports identified Lemos as a person of interest because he knew Jennifer, Jesten, and Matthew. Witnesses also told police he had taken a handgun from property associated with Sean.
Lemos was arrested on March 25, 2021, on an unrelated drug warrant. Grants police publicly emphasized that he was a person of interest, not a murder suspect.
Investigators later said Sean had tried to direct suspicion toward Lemos. Lannon even admitted that he had intended to return to New Mexico and kill him.
The homicide evidence ultimately centered on Sean Lannon alone. No public record established that Lemos participated in the five murders for which Sean was convicted.
That matters because the original investigation was full of people who looked suspicious for understandable reasons. Some lied. Some handled property. Some used drugs with the missing victims. Some avoided detectives or had outstanding warrants.
Suspicious behavior did not make them murderers.
The New Mexico Guilty Pleas
For years after the killings, Sean Lannon still faced the New Mexico homicide cases while serving or awaiting service of his New Jersey sentence.
The cases finally resolved in 2024.
On May 16, Lannon pleaded guilty to second-degree murder in the death of Randal Apostalon and received a 15-year sentence.
The remaining cases involving Jennifer Lannon, Jesten Mata, and Matthew Miller were also resolved through guilty pleas to second-degree murder. By early June, those three counts had produced another 45 years: 15 years for each victim, consecutive.
Together, the four New Mexico murder sentences total 60 years.
Reporting on the plea agreement states that Lannon is to serve his 35-year New Jersey sentence first and then return to New Mexico to serve the 60-year term.
The practical reality is that Sean Lannon, born in 1974, received a sentence structure extending far beyond an ordinary human lifespan.
What the Case Actually Proved
The Sean Lannon case is easy to sensationalize because of the number of bodies, the airport discovery, the dismemberment, the multi-state flight, and his later claim of 11 additional killings.
But the most important part of a factual retelling is separating what looked suspicious from what was eventually proved.
Matthew Miller did not simply vanish into a drug binge. He was murdered.
Jennifer Lannon and Jesten Mata were not hiding in Arizona. They were murdered.
Randal Apostalon was not part of a conspiracy to transport bodies. The evidence and Lannon's own plea established that he became another victim after being pulled into the effort to move the containers.
Michael Dabkowski was not merely the subject of one of Sean's stories about the past. He was killed in New Jersey, and Lannon pleaded guilty to first-degree murder.
Daniel Lemos and the other people questioned in Grants were not convicted as accomplices in the murders.
And the supposed 11 additional killings have never been proven.
The strongest evidence was not one dramatic clue. It was accumulation: Matthew's disappearance, his abandoned truck, surveillance footage, inconsistent accounts, Sean's use of vehicles belonging to other people, the discovery at the Sunport, airport video, the New Jersey homicide, and finally Lannon's own detailed admissions.
Why the Missing-Person Investigation Took Time
In hindsight, the clues around Sean Lannon can look obvious. Matthew's truck was near people connected to Sean and Jennifer. Sean used that truck. Jennifer, Jesten, and Matthew all disappeared within a narrow window. Sean's explanations shifted around drugs, Arizona, errands, and other acquaintances. But detectives did not have the benefit of knowing how the story would end.
At the beginning, each missing person had circumstances that could support a noncriminal explanation. Matthew had a history of drug use and had contacts throughout a small community. Jennifer's relationships were complicated, and people around her believed she sometimes left town. Jesten belonged to the same social network and was also difficult to locate. In a case like that, police have to prove more than that someone's behavior feels wrong.