The 21-year-old suspect in the July Fourth parade mass shooting in Highland Park, Illinois, was charged Tuesday with seven counts of first-degree murder.
Eric Rinehart, the Lake County State Attorney, told reporters he will request a judge to hold Robert "Bobby" Crimo III while the investigation continues. If convicted, the suspect faces up to life in prison without parole.
"I want to emphasize that there will be more charges. We anticipate dozens of more charges centering around each of the victims, psychological victims, [and] physical victims," Rinehart said.
"We will seek the maximum sentence against this offender. Not because we seek vengeance, but because justice and the healing process demand it," the state attorney added
The update in the investigation came after a seventh victim died Tuesday from injuries sustained in Monday's mass shooting.
Related video: 7th victim dies after shooting at Illinois Independence Day parade
Authorities believe the massacre had been planned for weeks, and they say more than 70 rounds were fired from the gunman's high-powered rifle, which was similar to an AR-15.
The suspect is accused of opening fire from a roof of a business, which he accessed from a fire escape ladder, police said.
Police said Crimo wore women's clothing during the shooting to apparently allow him to hide his facial tattoos and blend in with the crowd to flee.
"Following the attack, Crimo exited the roof, he dropped his rifle and he blended in with the crowd and he escaped," police said Tuesday. "He walked to his mother's home, who lived in the area, and he blended right in with everybody else."
It appears Crimo bought the rifle legally in Illinois, police said.
Police said they are looking to talk to a witness who is believed to have seen Crimo drop the rifle behind a red blanket immediately after the shooting.
Crimo bought five guns overall, including two rifles, over the last year or so, police said.
No motive is known, police said. When asked by reporters if the gunman targeted anyone specifically, police said the "shooting appears to be completely random."
Crimo — who was apprehended Monday evening after an hours-long manhunt — is answering questions from investigators and has made statements taking responsibility for the attack, according to multiple law enforcement sources.
In 2019, a family member reported that Crimo said he was going to "kill everyone" at the home, police said Tuesday. Authorities confiscated knives, a dagger and a sword at the time, police said.
There was no information that he possessed any guns at that time and there was no probable cause for arrest, police said.
Crimo is believed to be linked to social media posts that discuss or depict acts of violence, including shooting people, a law enforcement source briefed on the case told ABC News.
Online posts include a video showing what appears to be a portion of the same parade route where the shooting took place.
In a video posted more than a year ago to his YouTube page, Crimo is shown in what appears to be a depiction of the aftermath of a school shooting.
Crimo had been living with his uncle, Paul Crimo, but the two barely interacted beyond exchanging hellos, Paul Crimo told ABC News.
Paul Crimo said he last spoke to his nephew the evening before the shooting and said he was shocked to learn about his alleged involvement.
He described his nephew as quiet and respectful and said the 21-year-old never mentioned firearms.
Rinehart told reporters there was no application to get a court order to take away the suspect's weapons following his past allegations.
However, he emphasized that the state's "red flag" laws, under which a family member can ask a judge to take a person's firearms away if they think they pose a risk, keep communities safe and pushed for a bigger awareness of those laws.
"We must vastly increase use of the Illinois red flag law," he said.
Rinehart also called for a ban on assault rifles.
"Studies have shown that mass shootings like what happened yesterday went down during those 10 years, we should have that same ban in Illinois, and beyond in the entire country," he said, to applause from the crowd.
The state attorney said the investigation is ongoing and asked anyone with information or footage from the scene to call his office.
The mass shooting broke out when the suburban Chicago parade was about three-quarters of the way through Monday morning, authorities said.
About 38 people were injured.
Revelers fled in panic, leaving behind empty strollers, overturned chairs and half-eaten sandwiches.
When the gunfire erupted, parade-goer Zoe Nicole Pawelczak grabbed her dad and started running through the sea of people.
"I saw multiple people slaughtered," she told ABC News.
"Everybody is crying. We ended up making it behind a corner and we hid behind a dumpster. This man was there with his two very young children and he had put them in the dumpster for safety," she said.
Pawelczak said the man wanted to leave to find his other son, and asked her to watch the two children in the dumpster.
"So I watched his kids for him," she said. "They were like, 'What's going on?' And I was like, 'It's just fireworks, it's OK,' just trying to keep them calm."
Dr. David Baum was watching his grandson, daughter and son-in-law march in the parade when the gunfire began.
"Bodies were horribly, horribly, horribly injured from, you know, guns and bullets that were made for war — not for parades," Baum said of some of the victims.
"The paramedics went quickly and assessed the damages — saw bodies that were blown apart and put a blanket over them quickly. And then went on to try and help other people," he told ABC News. "These are injuries that nobody should have to see."
Crimo was at large for hours after the shooting. After police released an image of Crimo and his car Monday evening, he was spotted driving and led police on a brief pursuit, authorities said.
He was stopped at U.S. Highway 41 and Westleigh Road in Lake Forest, Illinois, where he surrendered, according to police.
A second weapon, also purchased legally by Crimo, was found in the car, police said.
On Tuesday evening, Steve Greenberg, an attorney representing the suspect's parents, released a statement from the couple saying their "hearts, thoughts and prayers go out to everybody."
"We are all mothers and fathers, sisters and brothers, and this is a terrible tragedy for many families, the victims, the paradegoers, the community and our own," the statement read.
President Joe Biden said in a statement that he "surged Federal law enforcement to assist in the urgent search for the shooter."
"Members of the community should follow guidance from leadership on the ground, and I will monitor closely as we learn more about those whose lives have been lost and pray for those who are in the hospital with grievous injuries," Biden said.
He noted that he recently signed into law the most significant gun control legislation in decades, adding, "But there is much more work to do, and I'm not going to give up fighting the epidemic of gun violence."
Vice President Kamala Harris said in a statement, "On what should be a celebratory day with family and friends, we are grieving the lives that were taken in another act of senseless gun violence."
"More should be done to address gun violence in our country," she said. "President Biden recently signed into law the first major bipartisan gun reform legislation in almost 30 years — and we will continue fighting to end this senseless violence."
An impassioned Illinois Gov. J. B. Pritzker said, "It is devastating that a celebration of America was ripped apart by our uniquely American plague. A day dedicated to freedom has put into stark relief the one freedom we as a nation refuse to uphold: the freedom of our fellow citizens to live without the daily fear of gun violence."
"I'm furious that yet more innocent lives were taken by gun violence. I'm furious that their loved ones are forever broken by what took place today. I'm furious that children and their families have been traumatized," he said. "While we celebrate the Fourth of July just once a year, mass shootings have become our weekly — yes, weekly — American tradition. There are going to be people who say that today is not the day that now is not the time, to talk about guns. I'm telling you there is no better day and no better time than right here and right now."
"Our founders carried muskets, not assault weapons. And I don't think a single one of them would have said that you have a Constitutional right to an assault weapon with a high-capacity magazine — or that that is more important than the right of the people who attended this parade today to live," the governor added.
Representatives of the gun reform group March For Our Lives, founded by survivors of the 2018 high school mass shooting in Parkland, Florida, said in a statement, "Just three weeks ago, young people organized a March For Our Lives in Highland Park, along with communities across the country."
"We are grieving for the horrific loss of life in Highland Park, and the carnage brought on by a high-powered rifle," they said. "We wish eternal peace for those who were murdered, and we will fight like hell for the living."
New Jersey Gov. Phil Murphy is among the leaders reacting to the nation's latest mass shooting, tweeting, "Not even a parade on the Fourth of July celebrating our nation's independence is immune from our nation's gun violence epidemic. Tomorrow, I will sign seven sweeping commonsense gun safety bills into law. We cannot wait."
Secretary of Homeland Security Alejandro Mayorkas said in a statement that the U.S. must "address the epidemic of targeted gun violence, including the development and implementation of new community-based models of prevention and intervention."
"The Department of Homeland Security will redouble its work in this critical area and help lead the effort to prevent violence," he vowed.
ABC News' Josh Margolin, Pierre Thomas, Aaron Katersky, Alex Perez, Jack Date, Will Steakin, Jeff Cook, Will McDuffie and Caroline Guthrie contributed to this report.