In an article from the Star Tribune five sources are used.
The first source is the police, the second is the victim's father, and the rest are neighbors of the victims. Each of the four individuals is named.
The sources are used scattered throughout the story, with the most credible (police and family) being used first.
The information straight from the three neighbors is clustered together towards the end of the story.
It seems that most of the information is from people, but some must come from records.
The reporter sets up attribution by giving the information and then telling readers who said it. The reporter also uses several direct quotes from individual people.
The way she set up the attribution was effective, and was not confusing. It was very straightforward.