The would-be robber, according to the account provided by Fairfax County police, made at least two mistakes. He went into the wrong person’s apartment, and he entered an apartment where he was badly outnumbered.

It was about 20 minutes after midnight on Thursday when the would-be robber went into an apartment in the 4100 block of Wadsworth Court, the police said in an account provided on Friday.

According to the account, he entered “demanding money.” When the victim said he had none, police said the intruder tried to stab him with a knife. They said the victim’s roommates tackled the intruder and held him for police.

Police said 22-year-old Diallo Duffin of Annandale was charged with robbery and malicious wounding.

In the statement, police said the investigation showed the apartment was entered in the belief “it belonged to someone else.”

The victim was treated at the hospital for injuries that were not life threatening, police said.

The site is in the Annandale area, east of the Capital Beltway and north of Route 236.