A child injured when a car plowed into a Christmas parade in the US state of Wisconsin has died, taking the toll from the tragedy to six, a local prosecutor said Tuesday as the suspect appeared in court.

Darrell Brooks, 39, was charged with five counts of intentional homicide, and now faces a sixth murder charge, prosecutor Susan Opper said. 

Brooks allegedly steered his red SUV into marching musicians, dancers and children in the annual holiday parade Sunday in the city of Waukesha, sparking fears of a possible terrorist incident. 

Tensions were already running high in the Midwestern state following a high-profile acquittal in the racially charged trial of Kyle Rittenhouse, a teen who fatally shot two people during Black Lives Matter protests in nearby Kenosha last year.

The child who died was identified by his parents on a GoFundMe page as eight-year-old Jackson Sparks.

"This afternoon, our dear Jackson has sadly succumbed to his injuries and passed away," wrote Aaron and Sheri Sparks.

They said their 12-year-old son Tucker was also injured at the parade, but was "miraculously recovering" and will be discharged from the hospital.

In addition to Sparks, four women and one man were killed and 62 people injured, including other children, some still in critical condition.

Given the number of injured, Opper said, "There are a number of other charges that we are reviewing and considering."

"But certainly at the very least we do intend to file a sixth count of intentional homicide," she told the court.

- Multiple life sentences -
Brooks appeared in court for his arraignment wearing what appeared to be body armor. His face was masked, hands cuffed and head bowed as a judge said he faced multiple life sentences if found guilty for the deaths.

Waukesha officials said there appeared to be no motive for the disaster, other than that Brooks had driven away from some kind of confrontation as police were called to the scene.

Court commissioner Kevin Costello set Brooks' bail at $5 million as his court-appointed attorney said he was "indigent."

"The nature of this offence is shocking," Costello said.

He added two detectives had tried to stop Brooks but that he continued, appearing to intentionally aim at people and swerving from side to side as he drove through the parade.

"You are presumed innocent sir, but that's what the allegations are," said Costello.

" I have not seen anything like this in my very long career. It seems to be a very strong case for the state."

Questions have been raised meanwhile as to why Brooks, who was arrested in nearby Milwaukee just weeks earlier on multiple charges of domestic abuse for hitting and running over the mother of his child, had been released on a minimal bail of $1,000.

Opper recounted to the court a lengthy record of arrests and jumping bail for Brooks going back to 2000.

In Wisconsin he had been charged multiple times for minor drug offenses, resisting arrest, weapons charges, and not paying child support, and had served several short stints in jail.

He was convicted in Nevada in 2006 and 2007 for domestic battery and " statutory sexual seduction," or sex with an underage girl.

Earlier this year he was jailed in Georgia for battery and family violence.

"There are not words to describe the risk that this defendant presents to our community," Opper said, asking for the high bail level.