One of the three teenagers convicted of starting a house fire in the wrong home, killing a family of five, will serve 40 years in prison for second-degree murder.

“This is the worst and most senseless murder I’ve ever investigated,” Denver Police Department Detective Neil Baker said at the sentencing on Friday.

Gavin Seymour, now 19 years old, was sentenced by Judge Karen Brody in a Denver District court on Friday afternoon for second-degree murder in connection to the deaths of Djibril Diol, 29; Djibril’s wife, Adja, 23; the couple’s 2-year-old daughter Khadija; Djibril’s sister, Hassan, 25, and Hassan’s 6-month-old daughter, Hawa Beye.

“This monster didn’t just kill five people,” Amadou Beye, father of Hawa Beye, said during the sentencing. “He destroyed me. He destroyed my family.”

The arson at the Senegalese immigrant family’s home in the Green Valley Ranch neighborhood of Denver on Aug. 5, 2020, began as a miscalculated revenge plot.

In the early morning, Seymour, Kevin Bui and Dillon Siebert — Bui and Seymour 16 at the time, Siebert 15 — allegedly started a house fire as an act of revenge for a stolen iPhone. 

The trio broke into the home in masks and poured fuel around the first floor, lighting it ablaze.

Five of the eight people in the house died. The three that escaped — the owner of the home, his wife and child — suffered broken bones and trauma after jumping from the third-story window.

After the teens were arrested by the Denver Police Department in January 2021, Bui told investigators he had been robbed the month before the fire. He then traced his iPhone to the home, according to court records. He admitted to setting the fire, only to find out the next day through news coverage that the victims were not the people who robbed him, according to police.

The trio allegedly didn’t tell the police about the incident, despite seeing news that investigations had begun. Bui and Seymour allegedly went on two vacations after the fact and before their arrests.

Bui and Seymour planned the fire for three weeks, according to Courtney Johnston, the lead prosecutor in the case. Bui even Googled the floor plan of the house. 

The duo texted about the fire during that period, according to Baker. Bui even sent Seymour a text message that read, “#possibly ruin our futures and burn his house down.”

Seymour’s attorney, Jenifer Stinson, and a collection of seven character witnesses and family members all spoke out for the teen, claiming that he is a compassionate person that has suffered from trauma and learning disabilities, making him more susceptible to peer pressure.

They also argued that he did not have a fully developed brain, with the incident occurring three days after his 16th birthday.

Stinson claimed that Bui was the “ringleader” and that Seymour just followed along.

“He knows he has a steep price to pay,” Seymour’s mother, Stephanie Tyler said as Seymour looked at the ceiling, clamping his eyes shut to hold back tears.

“But, I’m going to ask you to please consider who he is as a whole person, including his potential for redemption,” she added.

The victims’ side, filled with just as many representatives — stretching all the way to Senegal — argued that Seymour’s actions were more than just the impulse of a 16-year-old kid. 

“I don’t hate you. I don’t dislike you,” Samba Ba, family friend of the victims, said. “But, where was that compassion? Where were all those things that people are saying about you when you were entering and pouring fuel inside someone’s house? Even if no one was in that house, people paid for these houses. People put their lives in these houses.”

During the investigation, the arson struck fear in the West African community in the city, something the victims were a significant part of. Before the incident was deemed a mistargeting, many believed it may have been an act of racism and violence toward the community, according to Johnston. 

Regardless, the community still mourns Djibril Diol — a family friend, best friend and brother to every person that attended the sentencing. 

Seymour pleaded guilty to second-degree murder charges in January, 2024, agreeing to a maximum sentence of 40 years. 

And though he will now serve the max sentence, it’s still not enough. 

“No matter anything they say, we can’t get five people back,” family friend Ousman Ba said after the sentencing. “A mother, a father, a community leader. We can’t get these people back.”

The tight Senegalese community still has one battle ahead. 

Siebert pleaded guilty to second-degree murder and received a 10-year detention sentence that includes three years in the state’s Division of Youth Services, which handles juvenile detention, and seven years in the Department of Corrections’ Youthful Offender System.

Bui is set to appear for an arraignment on March 21. 

“Please know that I have to live with the decision I made that night for the rest of my life. And if I go back and prevent all this, I would,” Seymour said moments before the final sentencing.

Seymour will now spend double his current lifespan in prison.