Detroit ? Two thrill-seeking teenagers stabbed an adult acquaintance, took a blowtorch to his corpse and threw his severed head into a river, prosecutors said Monday as they charged the pair.

Canton High School senior Jean Pierre Orlewicz, 17, and Alexander James Letkemann, 18, ambushed 26-year-old Daniel Sorenson on Wednesday in a garage owned by Orlewicz’s grandfather, Wayne County Prosecutor Kym Worthy said. A tarp had been spread on the floor, she said.

“They lured him in the garage, where they prepared a space to kill him,” Worthy said at a news conference.

Sorenson, who had worked as a bouncer, was stabbed multiple times in the back, his head sawed off and his body wrapped in the tarp, authorities said. Orlewicz and Letkemann burned his hands and feet with a blowtorch, possibly in an effort to conceal his identity, Worthy said.

“They made plans on how they were to clean up the blood,” she said. “They made plans on how they were going to dispose of the body.”

The teens loaded Sorenson’s torso in a pickup truck, took it from the garage in Wayne County’s Canton Township, drove it about seven miles to a cul-de-sac in Northville Township and set it on fire using gasoline, police said. A utility crew found it Thursday morning, police said.

Sorenson’s head was found Saturday in the Rouge River on the border of Detroit and Dearborn Heights, about 15 miles from where the torso was found.

Sorenson’s history as a registered sex offender in Michigan and Illinois and the fact that he may have owed his attackers a small amount of money appear to have had nothing to do with his death, Worthy said.

Sorenson was convicted in Illinois when he was 17 of having sex with a 14-year-old girl, said Northville Township police Lt. Greg Rhodes.

“We’ve all seen a lot. We’ve seen it all,” Worthy said of the Sorenson case’s investigators. “Still, a crime like this surprises us all.

“Anytime anyone kills just because they want to, and that’s what the evidence seems to suggest here, is bone-chilling. Why anyone would want to do that, especially being 17 years old, it makes us think and ask a lot of questions about our society.”

Other people may have been involved, Worthy said.

Raymond Cassar, Letkemann’s attorney, urged the public not to rush to judgment. He said Letkemann’s only other brush with the law came a couple of years ago when he was charged with being a minor in possession of alcohol.

James C. Thomas, Orlewicz’s lawyer, declined to comment.

Orlewicz, of Plymouth, and Letkemann, of Westland, were arraigned Monday on one count each of first-degree premeditated murder, felony murder and mutilation of a corpse. Not guilty pleas were entered on their behalf, and both were ordered held without bond and are due in court next Monday.

The murder charges carry mandatory sentences of life in prison. Mutilating a corpse carries a maximum sentence of 10 years.