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

In his first comments on the deadly crash, President Joe Biden said Monday, "While we don't have all the facts and details yet, we know this morning that five families in Waukesha are facing fresh grief of a life without a loved one."

"At least 40 Americans are suffering from injuries, some of them in critical condition, and an entire community is struggling, struggling to cope with the horrific act of violence," Biden said.

"Last night, the people of Waukesha were gathered to celebrate the start of a season of hope and togetherness and Thanksgiving," he continued. "This morning, Jill and I and the entire Biden family, and I'm sure all of us, pray that that same spirit is going to embrace and lift up all the victims of this tragedy, bringing recovery from the injuries and wrapping the families of those who died in support of their community."

The administration is "monitoring the situation very closely," Biden added.

-ABC News' Sarah Kolinovsky