The man, a resident of Borås in western Sweden, is suspected of having stabbed and beaten his grandmother in October of last year before suffocating her to death by rolling her head up in a rug, the local Borås Tidningen (BT) reported.
After allegedly killing his grandmother, the man then took her mobile phone and drove off in her car only to later run off the road.
He then called his mother, who came to pick him up.
The 22-year-old then explained that something terrible had happened to his grandmother.
The man's mother called the police, who subsequently found the 84-year-old with stab wounds and head trauma. She also had her head tightly wrapped up inside a rug.
The 22-year-old was arrested later that evening and remanded in custody several days later.
Investigators found traces of the 22-year-old's DNA on the shaft of a knife believed to be used in the deadly attack, as well as blood from the 84-year-old grandmother on the man's clothes.
While the grandson has admitted he was present at his grandmother's home, he has yet to provide a full account of what took place, despite several interrogations.
The man was said to have a good relationship with his grandmother, but prosecutors believe the 84-year-old's refusal to lend her car to her grandson, who was under the influence of drugs and alcohol at the time, may have led the 22-year-old to kill her.
“One can only speculate as to why he was so determined to borrow the grandmother's car. An educated guess could be that drugs may have had something to do with it,” prosecutor Daniel Edsbagge told BT.
In filing the murder charges on Monday, Edsbagge said he believed he had “solid evidence” implicating the 22-year-old in his grandmother's death.
According to BT, the man had been charged with a number of other crimes earlier in the year, including attempted assault, petty theft, and a number of drug offences.