MESA, AZ – A man convicted in a fatal shooting sparked by jealousy at a Mesa pizza shop was sentenced to life in prison this week, concluding a case that shook both a workplace and a family.

Tyler Ross McGuire, 31, received a life sentence without the possibility of parole after a Maricopa County judge ruled on his conviction for first-degree murder in the death of co-worker Deazo Seghi. Authorities said McGuire harbored an obsession with a female employee, leading to a deadly act fueled by jealousy and anger.

The fatal encounter stemmed from McGuire’s growing fixation on a woman he supervised at the pizza shop. According to investigators, he confessed to the woman that he had romantic feelings for her, but she rejected his advances. Not long after, McGuire confronted Seghi, convinced that his colleague was also interested in the woman. Tensions reportedly escalated over the following months, with McGuire’s hostility toward Seghi mounting.

Prosecutors revealed that the situation worsened as McGuire not only continued his obsession, but took steps to plan his attack. He purchased a firearm and went so far as to search out Seghi’s address.

The violence culminated nearly a year after McGuire’s initial confrontation with Seghi. On December 11, 2023, Seghi was found lifeless in his car outside an apartment complex near North Stapley Road and East Brown Road in Mesa. Witnesses recalled seeing McGuire approach the vehicle and fire multiple shots at Seghi before fleeing on foot.

Law enforcement tracked down McGuire soon after the shooting. A search revealed both a cellphone and the same black handgun used in the killing. Forensic analysis confirmed that the bullets fired matched shell casings at the scene, further tying McGuire to the crime.

The investigation took an unexpected turn days later when McGuire’s mother discovered his diary while cleaning. She contacted authorities, turning over pages that authorities said detailed his intent to murder Seghi and his rationale, including passages expressing deep-seated anger and fixation over the woman. In one entry, McGuire wrote about a decision to kill someone who had “hurt” him, and in another, he lamented losing what he believed was his chance at a relationship.

During trial proceedings, the jury found the evidence compelling, resulting in the first-degree murder conviction earlier this month. Prosecutors described the crime as a calculated and unprovoked act, emphasizing the irreparable loss suffered by Seghi’s family.

The sentencing marks the end of a case that highlighted the tragic consequences of fixation and workplace jealousy turning violent. McGuire is expected to serve his life sentence in an Arizona state prison.