A 19-year-old has admitted to killing his grandmother in her St. Cloud home by cooking up an oily marijuana concoction in the basement and setting the house ablaze in the process.

A jury trial for Dustin R. Zablocki, of St. Cloud, was scheduled to begin Tuesday, but he pleaded guilty in Stearns County District Court to aiding and abetting third-degree murder in the death of 85-year-old Sally A. Douglas in late 2014.

By pleading guilty last week, Zablocki has agreed to a seven-year sentence, with credit for time served. The last third of his sentence will be served on supervised release. A more serious third-degree murder charge, which carried a stiffer potential sentence, was dismissed.

Pleading guilty earlier to the same lesser charge was Justin E. Pick, 20, of nearby Sartell, who was with Zablocki at the time. Pick was granted a downward departure from state guidelines and sentenced to the seven months of jail time already served as well as 25 years of supervised probation.

Kenneth Wilson, Zablocki's attorney, said Tuesday his client got a stiffer sentence because he used an illicit drug after his arrest and while out on bail. That violation sent him back to jail on April 15, 2015.

Also, Wilson added, the prosecution contended that Pick "was lesser involved" in starting the fire. Pick also cooperated with investigators.

Wilson said he disagreed that Pick was not as responsible as his client for the fire and Douglas' death. "I'm a little upset with that," Wilson said.

Zablocki and Pick were making marijuana wax, aka "dab," in the basement on a hot plate on Nov. 22, 2014. Fire broke out, but neither called 911 after fleeing nor checked to see whether anyone else was home.

Zablocki was speaking to a police officer as his grandmother — found facedown near the front door — was brought outside wrapped in a blanket.

The grandson fell to his knees crying in anguish. "I just killed my grandma," he said to the officer, according to the criminal complaint filed against him.

Wilson said Tuesday that his client "thought his grandma wasn't home."

Douglas died Dec. 8, 2014, at Hennepin County Medical Center in Minneapolis from the smoke she inhaled during the Nov. 22 explosion and fire at her home in the 1900 block of 1st Avenue N.

Douglas' life in central Minnesota included operating a bait shop, waiting tables and filling orders at a small-town department general merchandise store. At the time of her death, she left behind four children, 13 grandchildren and 17 great-grandchildren.

Dab is known for its high concentration of THC, the active ingredient in marijuana. The oily substance gives users a more intense physical and psychological high.

It goes by such names as butane hash oil, honey oil, butter oil, dab and 710 (spells out "oil" on a cellphone turned upside-down).

Fires, explosions, death and injuries have been reported across the country from making the substance.

Paul Walsh • 612-673-4482