Brooks has been charged with five counts of first-degree intentional homicide, according to a criminal complaint filed on Tuesday by Waukesha County District Attorney Susan Opper.
The complaint, filed in the Waukesha County Circuit Court, detailed that 62 individuals were injured - some remain in critical condition - and another five were immediately killed in the Sunday incident. The death toll has since climbed to six, according to prosecutors.
The sixth individual has been identified as a child, while the others killed were adults, aged between 52 to 81 years old.
Local investigators detailed that one officer discharged three rounds into Brooks' SUV after he broke through a police barricade. The suspect is believed to have been fleeing the scene of an altercation near White Rock School.
"As I continued to watch the SUV, it continued to drive in a zig zag motion. It was like the SUV was trying to avoid vehicles, not people," one witness told a detective, per the complaint. "There was no attempt made by the vehicle to stop, much less slow down."
Another witness recalled the same zig zag driving pattern, telling the detective that he felt it was "a direct intent to hit as many parade participants."
Brooks, a registered sex offender in Nevada, was formally charged for his alleged crimes during his first court appearance on Tuesday.
Bail has been set at $5 million by the court. Unlike many other jurisdictions that employ a 10% rule for release, bail must be paid in full before an inmate can walk free in Waukesha.
Commenting on the bail amount, Judge Kevin Costello argued that it was warranted due to the nature of the case and the suspect's rap sheet.
"It is extraordinarily high, but it is an extraordinarily big case," he said, noting that Brooks has an extensive history of breaking the law.
If convicted, the suspect faces up to life in prison. Wisconsin is not a US state that upholds the death penalty.