'I Needed to Kill Someone': Pizza Shop Supervisor Jailed for Life After Obsession With Co-Worker Turned Deadly

A pizza shop supervisor who became fixated on a female employee and convinced himself a male colleague was 'pursuing' her has been jailed for life for a planned and unprovoked killing, after a court heard chilling diary entries detailing his intent to murder.

The sentence was handed down at Maricopa County Superior Court, where a judge ordered the 31-year-old defendant to spend the rest of his natural life in prison for the 2023 shooting death of co-worker Deazo Seghi in Mesa.

A jury earlier this month found the supervisor guilty of first-degree murder, concluding the killing was premeditated and driven by obsession rather than any immediate provocation.

Obsession at Work Escalated Over Time

Prosecutors told the court the defendant, Tyler Ross McGuire, managed a local pizza shop where both the victim and a female employee worked. Over time, he became fixated on the woman he supervised and admitted to having a romantic interest in her.

According to a press release from authorities, the woman made it clear she was not interested. Despite this, the supervisor grew increasingly jealous and convinced himself that Seghi was also attempting to pursue a relationship with her.

That belief led to a physical confrontation at work and marked the start of a steady escalation in anger and fixation, prosecutors said. Over the following months, the supervisor's resentment towards the victim intensified rather than subsided.

Diary Revealed Premeditation and Motive

Investigators said the case took a critical turn after the defendant's arrest, when his mother contacted police about a diary she had discovered among his belongings.

The diary outlined a detailed plan to kill the victim and provided insight into his mindset. One entry read: 'I decided a while ago I needed to kill someone. This person hurt me.'

Another entry revealed his fixation on the female co-worker, stating: 'If I had my way, I'd be with her. Although that opportunity was stolen from me.'

Prosecutors said the writings confirmed the murder was planned well in advance. Court documents show the defendant had purchased a firearm and searched for the victim's home address prior to the shooting.

Fatal Shooting Outside Victim's Home

On 11 December 2023, Seghi was found slumped inside his vehicle outside an apartment complex near North Stapley Road and East Brown Road in Mesa.

Witnesses told police the attacker approached the vehicle and fired multiple shots into the victim's chest before fleeing on foot. Seghi died at the scene.

The suspect was located and taken into custody shortly afterwards. Police recovered a black handgun and a mobile phone at the time of arrest. Ballistics testing later confirmed the bullets fired came from the recovered weapon.

Prosecutors Cite 'Unimaginable Loss'

In a statement following sentencing, County Attorney Rachel Mitchell said the punishment reflected the seriousness of the crime and the devastation left behind.

'This defendant carried out a planned and unprovoked killing, leaving a family to endure an unimaginable loss,' Mitchell said, as cited by Law&Crime. 'This sentence delivers justice for the victim and affirms that this level of violence will be met with the strongest consequences under the law.'

The case has drawn attention to the dangers of workplace obsession and how unchecked fixation can escalate into lethal violence, leaving lasting consequences for families, colleagues and the wider community.