Federal judge sentences carfentanil dealer in 16-year-old girl’s overdose death

ANCHORAGE, Alaska (KTUU/Gray News) - A federal judge sentenced an Alaska man to 30 years in prison for providing a teen carfentanil, which led to her overdose death in 2024.

Sean Doylton Mobley, 45, appeared somber in a federal courtroom in Anchorage on Thursday as Judge Timothy Burgess handed down his sentence.

Mobley faced not only federal crimes but also state charges in the death of 16-year-old Alena Toennis.

As explained by the government, Mobley’s calculated guideline range for sentencing was 262 to 327 months. Both Mobley’s defense and the government jointly recommended an above guideline sentence of 360 months, which Burgess ultimately agreed with. He imposed 360 months in incarceration with lifetime supervision upon release.

The statutory maximum sentence for distribution resulting in death is life in prison, which many members of the Toennis family said they had wanted.

Alena Toennis’ sister, Elyssa Toennis, said she felt 30 years was not enough to replace the life that her sister lost, but ultimately respected the judge’s decision.

“I think that it doesn’t matter how many years they were going to charge him, regardless if they did life or 30 years, because they gave him 30 years. Alena would have had more than 30 years left of life. She was only 16. Thirty years, she would only be 46 and I think she would have had a lot longer than that,” Elyssa Toennis said.

“I know that the community and the outpour that we got, everybody felt like he deserved a lot more than 30 years,” Crystal Toennis, Alena Toennis’ aunt, said. “So, we were hoping for life.”

During Thursday’s sentencing, several family members gave impact statements, with Alena Toennis’ mother, Nicole McDonald, telling the judge by phone that she was just getting to know her daughter again before her death.

“My family is forever broken dealing with the grief that is never ending,” McDonald said.

Burganndy Cohen, a cousin, spoke in person about her relative’s “rambunctious, firecracker” personality, adding that she’ll always miss the special moments they spent together.

“Alena is more than a case number. She was a 16-year-old girl that trusted the wrong person,” Cohen said.

Following family impact statements, Mobley was given a chance to speak in court. Expressing his remorse, he said he wished the night had never happened.

“I’m willing to take responsibility. I was the adult in the situation,” Mobley said. “I apologize to the family. I know my apology doesn’t mean much. I wish it was me instead of her.”

In the first case of its kind in the state of Alaska, the judge spoke about the significance of carfentanil while handing down the sentence. He said it is 100 times more potent than fentanyl and 10,000 times more potent than morphine.

In closing, Burgess spoke about the severity of Mobley’s actions by continuing to sell drugs after abandoning Alena Toennis’ body while she was overdosing.

Burgess said it was his hope that whenever Mobley closes his eyes, he’ll “think about that girl for the rest” of his life.

Mobley was indicted federally on charges of distributing carfentanil to two individuals, resulting in the fatal overdose of a minor and the non-fatal overdose of an adult, to which he pleaded guilty in October 2025.

The federal charges consisted of one count of distribution of controlled substance resulting in serious bodily injury and death and one count of distribution of controlled substance resulting in serious bodily injury.

On the state’s side, attorneys said Mobley is expected to change his plea to guilty to the charge of first-degree misconduct involving a controlled substance. The original manslaughter and second-degree murder charges for the state were dropped due to the federal charges.

Additionally, in a separate federal case, Mobley was also sentenced on charges of being a felon in possession of a firearm in a separate January 2025 incident.

Burgess said the 30-year sentence will run concurrently with whatever the state charges end up being. Mobley is scheduled to be sentenced in his state case on Feb. 5.

In a statement, U.S. Attorney Michael J. Heyman for the District of Alaska called Mobley’s actions callous and without remorse.

“He peddled whatever he could get his hands on to make a quick buck, including deadly drugs, with zero regard for human life,” Heyman stated. “Let this be a warning. Whether you lead an international drug trafficking organization or are a street-level dealer, if you endanger Alaskans, the consequences will be severe.”

Mobley’s defense attorney declined to comment.

The sequence of events unfolded over two days in mid-November 2024, according to court documents. Mobley distributed what he believed to have been powdered fentanyl to an adult victim on Nov. 14.

The man overdosed and was revived with Narcan. An associate warned Mobley not to distribute the substance to anyone else given the severity of the overdose, prosecutors say.

Despite the warning, prosecutors said Mobley continued dealing drugs that same evening, meeting Alena Toennis at a gas station around 11:55 p.m. on Nov. 14.

Alena Toennis texted a friend that she was “banging one out with Sean,” slang for using drugs, according to court documents. Mobley then drove her to a remote ATV trail in Wasilla, arriving around midnight, prosecutors said.

Testing showed the substance that caused both overdoses was not fentanyl as represented, but carfentanil. According to the Drug Enforcement Administration, carfentanil is a veterinary sedative used for large animals. It is not approved for human use.

According to prosecutors, Alena Toennis used the carfentanil while in Mobley’s truck and fatally overdosed between 12 a.m. and 12:13 a.m. on Nov. 15.

Mobley then dumped her body on the ATV trail and left to continue distributing drugs, investigators said. A person walking a dog discovered Alena Toennis’ body later that morning.

The state medical examiner determined the cause of death was acute combined toxic effects of carfentanil and methamphetamine, with hypothermia as a contributing condition.

State prosecutors said cellphone records, surveillance video and text messages placed Mobley with the teenager during her final moments alive. The evidence includes messages between them discussing illegal narcotics, Alena Toennis’ phone movements that matched Mobley’s device and surveillance video showing his vehicle tracking her location.

The federal carfentanil distribution prosecution marks the first such case in Alaska, according to federal prosecutors. The state murder charge carries a potential life sentence as well.

Mobley has an extensive prior criminal history in Alaska, including convictions for forgery, theft, criminal trespass and misconduct involving controlled substances dating back to 2000, according to court records.