Ten of the 18 children taken to Children’s Wisconsin hospital were admitted to the ICU, including six children in critical condition, hospital officials said.

Three of the ICU patients are in serious condition and one is in fair condition.

Another eight patients were admitted in fair conditions and two of the 18 children have since been discharged, officials said.

The hospitalized children range in age from 3 to 16 and include three sets of siblings, officials said. Injuries include serious head injuries and broken bones.

Six children were sent to the operating room Sunday night and another two children will undergo surgery on Monday, officials said.

-ABC News' Josh Hoyos

Brayden Kowalski was at the parade in Waukesha, which he described as "a very loving community," when he "saw about a block away, the SUV hurtling towards me."

He pulled his nephews, ages 4 and 6, out of the vehicle's path at the last minute. The SUV was about 5 feet away, Kowalski said.

Kowalski said he "was fear-stricken, but I just, I tried the best I could to help," escorting people from the street over to the sidewalks.

Of the driver, he said, "I don't know if they were targeting people, but they for sure weren't dodging people. "

Based on video evidence and interviews, investigators' preliminary assessment is that the driver wasn't aiming at specific parade participants but was speeding through the route to flee an earlier incident, multiple law enforcement sources told ABC News.

Authorities scoured social media and other digital platforms associated with the person of interest overnight. At this point authorities have no reason to believe there is any connection to radicalization, extremism or the ongoing debate about the Kyle Rittenhouse verdict, the sources said.

-ABC News' Josh Margolin, Luke Barr, Aaron Katersky

An 81-year-old man, Wilhelm Hospel, and a 79-year-old woman, Virginia Sorenson, were among the five killed, police said at a news conference. The other victims were 71-year-old LeAnna Owen, 52-year-old Tamara Durand and 52-year-old Jane Kulich.

The suspect, 39-year-old Darrell Brooks, is charged with five counts of first-degree intentional homicide, police said. More charges are possible, police said. He's set to make his first court appearance on Tuesday.

The suspect was involved in a domestic disturbance minutes prior to the deadly crash, police said.

Besides the five killed, 48 were hurt when the suspect "intentionally drove his maroon SUV through barricades into a crowd of people," police said.

One officer fired shots to try to stop the driver, but stopped shooting because so many parade-goers were present, police said. No one was hurt by the gunfire and the officer is on administrative leave, police said.

Police said the suspect acted alone and this was not a terrorist event.

Officials said this "Norman Rockwell-type Christmas parade" has been held for decades.