Report: Teens Brendan Johnson and Cassie Rieb burned, tried to dismember his grandma's body

Update: Our original post about the arrest of Sterling teens Brendan Johnson and Cassandra Rieb for allegedly murdering his grandparents, Charles and Shirley Severance, contained plenty of unsettling information; see our previous coverage below. But claims from a newly released arrest affidavit in the case are infinitely more shocking.

Among the assertions: Shirley begged for her life while being repeatedly stabbed, and after she was killed, Johnson and Rieb tried but failed to chop up her body while she was being incinerated. Moreover, the murders were committed nine days before they were reported. Additional photos and details below.

A warning before we go on: Information from the arrest affidavit, shared by both 9News and 7News, may disturb some readers.

As we reported, Johnson called police on May 29 on a supposed medical call for his grandfather. Charles was dead upon the cops' arrival, and the fact that he had been killed a week-plus earlier goes a long way toward explaining why an autopsy didn't find immediate signs of trauma to his body.

In a subsequent interview, Johnson reportedly maintained that Charles had given him a couple of checks adding up to $4,500, as well as permission to use his 2009 Chevy truck. He's said to have used the money and vehicle to attend a concert in Denver during the days leading up to the body's discovery.

Shirley, for her part, was missing, and in a separate interview with investigators, Rieb allegedly denied knowledge of her whereabouts -- although the report quotes her as admitting that Johnson actually wrote and signed the checks supposedly given to him by Charles.

Armed with this information, the cops went back to Johnson. The affidavit says he and Reib subsequently confessed to killing the Severances, and their explanations about the botched process are chilling.

The murder plot reportedly came together in early May, with the goal focusing on Johnson collecting his inheritance early.

On May 20, the affidavit says, Johnson and Rieb entered the Severances' place, with him assigned to smother Charles and her tasked with doing the same to Shirley. But things didn't go as planned.

The document says Charles struggled so much that Johnson eventually had to choke him to death -- although the seventy-year-old may have suffered a fatal heart attack while fighting for his life. And Shirley was even less cooperative. She apparently tried to run away, and when she couldn't escape, she pleaded with the teens not to kill her and even offered them money to go away.

They didn't. Johnson reportedly allowed her to get some water -- but while she was drinking, he tried to cut her throat. Instead, he slashed her jaw, prompting Shirley to try fleeing again. She failed to get free, however, and Johnson is accused of repeatedly stabbing her as she pleaded for her life.

Finally, Johnson strangled Shirley with a string, the affidavit says. Investigators believe that's what finally killed her.

The teens took the couple's bodies to a bedroom and left them there until the next day, police say. After the cleanup at the murder site was complete, they used the truck to drive Shirley's body to Prewitt Reservoir, a short drive from Sterling. There, they're accused of dousing it with gas and setting it ablaze -- and while it burned, they tried to hack off an arm and a leg.

The body was initially buried in a reservoir fire pit. But they apparently didn't feel it was secure enough there, so they returned on May 28, dug it up and took it to a remote location in Nebraska before returning home. Johnson alerted the cops to Charles's death the next day.

Johnson and Rieb made their first court appearance yesterday, where they were formally charged with two counts apiece of first-degree murder, aggravated robbery and theft. On top of that, Johnson faces two forgery charges.

Look below to see a brief 7News update on the case, followed by our original post.

Continue for our previous coverage of the Brendan Johnson and Cassandra Rieb arrests, including additional photos and a video. Original post, 5:52 p.m. June 4: "The first rule of fight club, is meow, meow, meow. kitty kitty."

The line above is the most recent post shared on Facebook by nineteen-year-old Brendan Johnson. Two days later, Johnson called police about the death of his grandfather, Charles Severance, in his hometown of Sterling -- and his grandmother, Shirley Severance, was soon reported missing. Now, Johnson and his girlfriend, eighteen-year-old Cassandra Rieb, have been accused of killing the pair, with Shirley's remains having been found in two separate locations.

There's nothing particularly unusual about the Facebook pages of Rieb and Johnson. Hers includes a number of self-portraits like this one.... a few pretty landscapes and a February post announcing that she'd been hired as a cashier at Walmart.

His, meanwhile, sports pics like this one.... well as assorted family snapshots and some memes. Here's an example of the latter: Like Rieb, Johnson, too, lists himself as a Walmart employee.

As for Charles and Shirley, both seventy, neighbors who spoke with 7News describe them simply as a nice older couple quietly living out their golden years.

But something went terribly wrong.

Continue for more about the murder arrests of Brendan Johnson and Cassandra Rieb, including additional photos and a video. On May 29, according to the Sterling Police Department, a caller said to reside with the Severances at their 409 South Third Avenue home (he was later identified as Johnson) contacted authorities for what was described as a "medical call." Responding personnel soon found Charles's body.

An autopsy conducted on Charles the next day found "no evidence of injury or trauma," the SPD revealed. However, an addendum noted that the results of a toxicology report wouldn't be available for three to four weeks, hinting that authorities weren't convinced he died of natural causes.

Meanwhile, the search continued for Shirley, with family members sharing this photo on Facebook....

...and police circulating her driver's license image: Law enforcers reportedly conducted numerous interviews with Johnson during this period.

It's unclear at this point what information he may have imparted, but eventually, Shirley's remains were found in two different places: Prewitt Reservoir, not far from Sterling....

...and another location in Lorenzo, Nebraska.

Thus far, additional details about the cause of Shirley's death have not been released. But Johnson and Rieb have been arrested on charges that include suspicion of first-degree murder, robbery, forgery and theft. They're expected to make their initial court appearance later this morning.

Look below to see booking photos for Johnson and Rieb, followed by a 7News report.

Send your story tips to the author, Michael Roberts.

More from our Colorado Crimes archive circa January 2013: "Greg Smith, convicted teen murderer, took pics of great grandparents after killing them."

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Michael Roberts has written for Westword since October 1990, serving stints as music editor and media columnist. He currently covers everything from breaking news and politics to sports and stories that defy categorization.
Contact: Michael Roberts