The driver who drove his vehicle into a Christmas parade in the American city of Waukesha, Wisconsin, was on the run from a crime elsewhere.
The parade would not have been a target, American media report, based on sources at the police and the judiciary.
They point to preliminary results of the investigation based on video images and interviews with witnesses. The authorities also search social media and other digital platforms. So far, the researchers have no reason to believe that there is any connection with radicalization or extremism.
There would also be no connection with the controversial acquittal of Kyle Rittenhouse last week in Kenosha, 80 kilometres from Waukesha. Rittenhouse had shot and killed two people at an anti-racism demonstration, saying he was in self-defence.
At least five people were killed and more than 40 injured in the Waukesha massacre.