Daryl Brooks has been charged with five counts of premeditated murder while in court over the Christmas parade attack in Wisconsin.
Five people were killed and 62 injured in the chaos that erupted in Waukesha, Wisconsin, about 20 miles west of downtown Milwaukee.
Prosecutors announced during the hearing that there is now a sixth victim, a child, and that they intend to file an additional number of premeditated murders later this week.
If convicted, Mr. Brooks, 39, will face a mandatory life sentence.
Crowds gathered along Main Street for the parade when a red SUV drove through a series of barricades and slid across the parade road.
Commander Daniel Thompson reported that a Waukesha police officer fired his rifle in an attempt to stop the driver.
Prosecutors are expected to bring fewer other charges in relation to the people injured in the attack.
Newly filed court documents quoted a witness to the accident who told investigators: “As I continued to watch the SUV, I continued driving in a zigzag motion. It was as if the SUV was trying to avoid vehicles, not people. There was no attempt by the car to stop. Not to mention slowing it down.”
The criminal complaint does not provide any details about the actual arrest if Mr. Brooks made any statements to the police.
Ahead of the hearing, Commissioner Kevin Costello warned people in the courtroom to remain calm despite the allegations against Mr Brooks and leave if they are overcome with emotion.
The defendant appeared to be wearing a windbreaker as he was taken to court to sit next to his lawyer.
Investigators demanded a $5 million cash bail, saying it was “justified given his history” and calling him a “threat to our community.”
Commissioner Costello said he believed Mr Brooks was an escape risk and that he did not “perform well under pressure”.
“You don’t respond well to common sense within our community and our society,” he said as he released bail for $5 million
“I am an old man who has been doing this for nearly 40 years. The nature of this crime is appalling, and I was not expecting the details of it here today,” Commissioner Costello said.
Not only did two detectives try to stop this, but they expressed the opinion that this was a deliberate act.
“You’re supposed to be innocent, sir, but these are the allegations. I’ve never seen anything like this in my entire career and it seems to be a very strong case for the state.
“Bail is extraordinarily high but it is an extraordinarily large issue and there is an extraordinary history of this man who has hurt people and has not followed court orders, has not adhered to criminal laws or societal norms.”
The five victims who died were Virginia Sorenson, 79; Lana Owen, 71 years old; Tamara Durand, 52 years old; Jane Kulich, 52 years old; and Wilhelm Hospel, 81.
Among the wounded were poorer Catholics and members of the Milwaukee Dance Grandmothers.
Mr. Brooks was arrested earlier this month for using a 2010 Ford Escape to run over the mother of his child, according to court documents.
A criminal complaint in that incident stated that a woman told police that Mr. Brooks had stopped by her after a previous domestic dispute.
He told her to get in his car, and when she refused he hit her in the face with a closed fist, according to the complaint.
He was released on $1,000 bail on charges including domestic violence and charged with using a vehicle to cause injury, according to a criminal complaint.
Brooks is also a registered sex offender in Nevada, where he was convicted in 2006 of vaccinating a 15-year-old, according to ABC News.
Then he was arrested again in 2016 when he failed to comply with sexual offense laws.
Police in Sparks, Nevada, reported that the man saved the charge but did not return to court, and a warrant was issued in August 2016 for not appearing.