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Teen sentenced in case of Green Valley Ranch arson that killed Senegalese family in 2020

"They killed more than just five people," the victim's family said. "They killed a lot of us, too."
Diol house fire in Green Valley Ranch_flowers out front
Posted at 12:55 PM, Feb 01, 2023
and last updated 2023-02-02 15:10:42-05

A teenager was sentenced to seven years in district court — and three years in juvenile court, for a total of 10 years behind bars — in connection with a 2020 house fire in Denver's Green Valley Ranch neighborhood that killed a Senegalese family of five.

The fire was reported around 2:40 a.m. on Aug. 5, 2020 along the 5300 block of N. Truckee Street. Later that day, the Denver Fire Department confirmed a toddler, child, and three adults had died and investigators suspected arson. The family had immigrated to Colorado from Senegal.

About half a year after the deadly fire, in late January 2021, authorities arrested three teens in connection with the crime: Kevin Bui and Gavin Seymour, both 16 years old at the time of their arrest, and Dillon Siebert, who was 15 at the time of his arrest. The trio incorrectly thought Bui's stolen iPhone was in the home, according to an arrest affidavit.

Teen sentenced in case of Green Valley Ranch arson that killed Senegalese family in 2020

Due to his age, Siebert's name had not been released previously. That changed with the plea deal, when the case was adjudicated in adult court.

Siebert, who is now 17 years old, was initially charged with 47 different counts, including first-degree murder, attempted murder, first- and second-degree assault, arson, burglary and conspiracy.

On Dec. 9, 2022, he pleaded guilty to second-degree murder, including a sentence enhancer for using a weapon in a crime. The plea bargain between the defense team and prosecutors included adjudicating the case in district court — which is adult court — even though Siebert is a juvenile because of the heinousness of the crime.

On Wednesday, Siebert was sentenced, though it was somewhat complicated as it included both juvenile court and district court to satisfy the sentencing rules regarding incarceration.

He was sentenced to seven years in district court Wednesday morning, as well as a suspended sentence of 26 years should he violate the terms of that sentence, according to Denver District Attorney Beth McCann. He was also sentenced to three years in juvenile court Wednesday afternoon.

Green Valley Ranch arson august 2020

In district court in the morning, the defense said Siebert was deeply sorry for what had happened and had stayed patient, resilient and kind throughout the process since his arrest. He has shown the ability to change, the defense said, and has not had any incident reports in detention.

The defense claimed he was battling low self-esteem at the time and was desperate to make friends. He started spending time with Bui and Seymour in the summer of 2020 and when a revenge plot began to form over SnapChat, it included things like keying a car, throwing eggs and smoke bombs, but never burning down a house, the defense said. Siebert went with the wrong crowd that night, became intoxicated and it turned into a horrific tragedy, they said.

The guilt and shame of his actions weigh heavily on him, the defense said. He recognizes there is nothing he can do to make those impacted families whole again.

The defense rested after saying that the evidence against Siebert is "staggeringly different" than what it is for Bui and Seymour. They asked for a 10-year sentence.

Victims were then allowed to give their testimonies.

Abou Diol started, saying the fatal fire destroyed "the best of our family," and it doesn't make sense for a 14-year-old to go to a person's house at 2 a.m. drunk and kill people.

"If he gets out in 10 years, that's fine for him, but what about us? Our family is not coming back," he said.

One family member, who was in the house at the time of the fire and escaped, recalled opening a door, seeing the entire house in flames, and then leaping from a window and breaking his leg. He said his wife jumped from a window and broke her back.

"At this point, nothing more to say – we are behind God and we are behind the justice system," he said, and then looked at the judge. "You can make it better.... What they did to us, even if he's locked up for 100 years, it changes nothing for us."

A husband of one of the victims also spoke, and implored the courtroom to think of their own families.

"This guy is a monster," he said.

His 1-year-old daughter and wife were killed.

"She was my everything in my life," he said. "She was the most perfect woman I knew in this world. You took it away from me forever. Tomorrow was supposed to be my wife’s birthday."

"They killed more than just five people," he continued. "They killed a lot of us, too. Now we’re just trying not to think about killing ourselves every single day. But I won’t, because I don’t want to give them another victory. But I’m a dead man. I’m just standing in front of you trying to express myself, but I’m dead without my wife and daughter. I have nothing anymore."

A fourth family member said the family lived in fear for several months because they did not know who committed the crime.

"You cannot pursue a dream if you cannot sleep in peace," the family said. "The only thing you’ll have is a nightmare and that has been our lives."

They said they could not imagine Siebert being released in 10 years.

At his sentencing in district court, Siebert spoke for a minute or two, asking for forgiveness from the deceased victims and their families. He acknowledged he is fortunate to have his own family that loves him.

After he was sentenced, the victims' family members were upset with the proceeding and sentencing, saying it did not feel just.

The judge said that both sides had very intelligent attorneys and he had to accept their plea deal, even if the victims' family does not feel it is right.

Arson suspected after toddler, child, 3 adults die in Denver house fire Wednesday morning

On the morning of the blaze in 2020, Capt. Greg Pixley with the Denver Fire Department said firefighters arrived at the home just before 3 a.m. and made a valiant effort to try to help the people still inside from the "very significant fire." He confirmed five people had perished and three others, who had all been on the second flood, were able to evacuate on their own.

The deceased were later identified as Djibril and Adja Diol, their 2-year-old daughter Khadija, Hassan Diol and her infant daughter, Hawa Baye. Djibril “Jibby” Diol was working as an engineer on the Central 70 project after receiving his civil engineering degree from Colorado State University.

Diol Family

The same day as the fire, authorities said they suspected arson and within a few weeks, they had focused their efforts on identifying three masked people seen on surveillance footage in the area at the time.

Evidence showed the fire was started with gasoline and surveillance video depicted one of teens carrying a jug to the scene, according to an arrest affidavit. It also showed that the suspects entered the home at some point and gasoline was put on the interior walls on the first floor of the home, according to the affidavit.

No evidence has been found to show the Diol family had anything to do with the alleged robbery Bui described, according to a preliminary hearing held in November 2021.

Investigators in August 2020 released pictures of three people wearing full face masks and dark hoodies, and pictures of a dark-colored four-door sedan, that they say are connected to the investigation into a suspected arson that killed five people from a Senegalese family earlier that month.

As the months ticked by, authorities increased the reward for information to $50,000 in November 2020.

On Jan. 27, 2021, the Denver Police Department announced it had arrested Kevin Bui, Gavin Seymour, and the now-17-year-old. Bui and Seymour were 16 years old at the time of the fire. Siebert was 14.

Two teens charged as adults in connection to Denver house fire that killed Senegalese family

Bui and Seymour were formally charged as adults in early February 2021. They faced the same 60 counts, which includes five counts of first-degree murder after deliberation, five counts of first-degree murder (extreme indifference), five counts of felony murder, multiple counts of attempted murder, first-degree assault with a deadly weapon, first-degree arson, burglary and conspiracy, according to the Denver District Court.

During a preliminary hearing in November 2021, the lead detective in the case said Bui admitted to planning and executing the fire.

Investigators said the three boys had searched the Truckee Street house on Google multiple times in late July 2020. They also determined that Bui and a minor had purchased the masks seen in the surveillance footage at a Party City close to where they had lived. Cell phone data corroborated the Party City purchases and was used to track the suspects' movements from the Lakewood store to the Green Valley Ranch home hours later, investigators said in an arrest affidavit.

Bui told investigators he was robbed weeks earlier while trying to buy a gun in City Park. When he pinged the stolen iPhone to find where it was located, the Truckee Street address popped up. He claimed that's why boys went there to retaliate.

Police wrote in the affidavit that social media played a big role in helping investigators identify the suspects and determine a motive. Of the many SnapChats sent back and forth about the retaliation, Siebert was involved in about 2% of the conversations, while about 97% were between Bui and Seymour, according to both the defense and prosecution in Siebert's case.

Bui pleaded not guilty in August 2022. The month prior, he faced new charges tied to allegedly possessing and distributing pills with suspected fentanyl in jail.

In late January 2022, a judge denied attorneys’ requests to move the Bui and Seymour cases to juvenile court.

Denver judge rejects teens' request to move fatal house fire case to juvenile court

As of now, both Bui's and Seymour's cases are on hold while the Colorado Supreme Court reviews a hearing on the issue of a Google search warrant that allowed for a reverse keyword search, which ultimately led authorities to identify the three suspects. Their attorneys claim that the use of this search warrant was a violation of the protection of unreasonable search and seizures because it was too broad.

Both of them face longer sentences than Siebert, since they were both older and because they had a greater role, according to prosecutors.

In addition to the three juvenile suspects, a woman named Tanya Bui was arrested on Jan. 29, 2021 in connection with the fire. She faced federal charges of possession with intent to distribute less than 50 kilograms of marijuana and possession of a firearm in furtherance of a drug trafficking crime, according to federal court documents. According to an arrest affidavit, she was paying for a cell phone that belonged to a suspect in the arson investigation who had the initials KB. She was sentenced on July 15, 2022 to more than 10 years in prison after she pleaded guilty to federal firearm and drug distribution counts in February.

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