Police: Attribution

How do you know this?

DaRoza said that he swung the cane as hard as he could into Keel's face.

Is it because DaRoza said it to you?

No, it's not. It's because DaRoza told the cops, and the cops put it in their report. So, proper attribution would be something like this:

DaRoza said that he swung the cane as hard as he could into Keel's face, according to a sheriff's report.