The suspect in Monday's mass shooting at a July 4th parade in Highland Park, Illinois, that left seven dead and injured more than two dozen has been charged with seven counts of first-degree murder, Lake County State's Attorney Eric Rinehart announced during a news conference Tuesday evening. If Robert E. Crimo III, 21, is convicted, the charges could lead to a mandatory life sentence, Rinehart said. More charges are expected to come, Rinehart said, including attempted murder, aggravated discharge and aggravated battery charges. Crimo has been in police custody since being apprehended Monday evening. Attorney Steve Greenberg has been retained to represent Crimo's parents, Greenberg confirmed to CNN Tuesday evening in an email. The attorney released a statement on Twitter on behalf of the suspect's parents. "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. Our hearts, thoughts, and prayers go out to everybody," the statement read. Police earlier Tuesday identified six of the seven victims killed in the shooting. A total of 45 people died or were injured during the shooting, said Christopher Covelli, spokesperson for the Lake County Major Crime Task Force. The focus of the investigation for the last 36 hours was on the shooter, but has now shifted to "the victims and those left behind," Highland Park Mayor Nancy Rotering said during the news conference. The release of the victims' names comes after investigators revealed the suspected gunman may have planned the attack "for several weeks" and wore women's clothing during the shooting to conceal his identity and his facial tattoos, and to help him leave with the crowd that was fleeing in the shooting's wake, Covelli said. Covelli also revealed Tuesday that Crimo had two prior incidents with law enforcement. In April 2019, an individual contacted authorities about Crimo attempting suicide. Authorities spoke with Crimo and his parents, and the matter was handled by mental health professionals, Covelli said. Then, in September 2019, a family member reported that Crimo threatened "to kill everyone" and had a collection of knives, Covelli said. Police removed 16 knives, a dagger and a sword from their residence. Highland Park police reported the incident to Illinois State Police. "At that time there was no probable cause to arrest. There were no complaints that were signed by any of the victims," Covelli said. Shortly after the September incident, Crimo legally purchased five firearms -- a combination of rifles, a pistol and possibly a shotgun -- between 2020 and 2021, according to Covelli. In order to buy firearms in Illinois, individuals need a Firearm Owners Identification (FOID) card. Crimo was under 21, so he was sponsored by his father, state police said in a news release. Crimo's application was not denied because there was "insufficient basis to establish a clear and present danger" at the time. Investigators still are trying to determine a motive for Monday's shooting, Covelli said. The carnage punctuates an already bloody American spring and summer -- during the past 186 days, more than 300 mass shootings have happened in the US, according to data compiled by the Gun Violence Archive, a non-profit tracking such incidents. "There are no words for the kind of evil that shows up at a public celebration of freedom, hides on a roof and shoots innocent people with an assault rifle," Illinois Gov. J.B. Pritzker said Monday. "It is devastating that a celebration of America was ripped apart by our uniquely American plague." Details on what led investigators to believe the shooting was planned for weeks were not immediately made available. After the shooting, Crimo went to his mother's house in the area, and then took off in his mother's car, Covelli said. After police determined Crimo was a person of interest in the investigation and publicized his information and the car they believed he was in, someone saw the vehicle on US 41 and called 911, Covelli said. A North Chicago police officer then saw the vehicle, waited for backup, stopped the car Monday evening near Lake Forest, Illinois, and arrested Crimo, authorities said. Besides the rifle used in the shooting, which authorities found abandoned near the shooting scene, officers also found a rifle inside the vehicle, Covelli said. Crimo, a resident of the city of Highwood, near Highland Park, had purchased both weapons legally in the Chicagoland area, Covelli said, without elaborating. Other firearms were found in Crimo's Highwood residence, Covelli said. Among the seven people killed, five adults died at the scene and one in hospital, Lake County Coroner Jennifer Banek said. It is not yet clear how old the sixth and seventh victims were. 'Much more work to do' Last year was the worst year on record since the Gun Violence Archive began tracking mass shootings in 2014. There were a total of 692 mass shootings in the US in 2021, the non-profit says. The Highland Park attack comes after several recent mass shootings that shocked the nation, including an 18-year-old's racist attack at a New York supermarket that killed 10 and another 18-year-old's shooting at a Texas school that left 19 students and two teachers dead. In the wake of those massacres, President Joe Biden signed into law the first major federal gun safety legislation in decades, marking a significant bipartisan breakthrough on one of the most contentious policy issues in Washington. Biden held a brief moment of silence at the White House on Monday evening during a July Fourth picnic, noting that he'd spoken to Gov. Pritzker and Highland Park's mayor. "There is much more work to do, and I'm not going to give up fighting the epidemic of gun violence," Biden said in a statement released Monday. Vice President Kamala Harris visited Highland Park Tuesday after delivering a speech at the National Education Association earlier in the day. "We're here for you and we stand with you," Harris said, adding that the administration would continue to offer federal assistance. "We've got to be smarter as a country, in terms of who has access to what, and in particular, assault weapons." In 2013, Highland Park had passed a local ban on semi-automatic firearms with the capacity to accept more than 10 rounds of ammunition, following a series of mass shooting incidents around the country. On Tuesday, Mayor Rotering said Monday's shooting showed a need for strict gun laws nationally. What we know about the suspect Former classmates described Crimo Tuesday as an odd, soft-spoken kid who didn't participate in class or school activities and showed little interest in engaging with his peers. The few friends Crimo had tended to be troublemakers who seemed to relish the notion of being outsiders, a couple of his former classmates said. "They wanted to be the 'anti-' group, like the rebels," said Mackenzie, a former middle school classmate who asked to be identified only by her first name to protect her privacy. "The aura they presented was opposite, negative and harsh." Other classmates, who wished not to be identified, described Crimo as a skater kid who made DIY skateboard videos on YouTube all the time. Just before Crimo dropped out of Highland Park High in 2017, he splattered "Awake" stickers in the school's stairways and bathrooms, the former classmate said. Crimo made music under the name "Awake the Rapper." On Monday, Covelli said law enforcement officials "processed a significant amount of digital evidence," which helped investigators identify Crimo as the suspect. The suspect's uncle, Paul A. Crimo, told CNN he had spoken at length to law enforcement on Monday and described his nephew as a "lonely, quiet person." His brother, who is the suspect's father, ran for mayor against incumbent Rotering in 2019 and lost. "I'm so heartbroken for all the families who lost their lives," Paul Crimo said. Stories of terror Witnesses told stories of sheer terror following the shooting in the affluent Chicago suburb. Some bystanders initially thought the sound of gunfire was fireworks, until many fled in terror. Eyewitnesses described grabbing their children and families and running for their lives, some hiding behind dumpsters or in nearby stores for safety amid the chaos. One paradegoer described seeing someone shot and killed, another saw a man shot in the ear with blood all over his face. Barbara Medina told CNN Tuesday her arm was broken during the stampede when bullets rained down on the parade. She was marching in the parade holding the banner for Community Partners for Affordable Housing (CPAH) when she heard gunshots ring out. A sea of people rushed toward her, so she dropped the banner, grabbed her 7-year-old daughter Caroline and her scooter and ran. She was separated from her 12-year-old son and her father in the chaos. Jonathan Birnberg, 41, told CNN Tuesday he attended the parade this year with his wife, 9-year-old son and 7-year-old twins. "The parade is a big tradition and didn't happen the last two years, so everyone was really excited. There's a carnival after and fireworks tonight, and there was excitement about bringing those traditions back," Birnberg said. When the gunfire began, he said nobody moved at first, unaware of the meaning of the noise. During a second round of shots, though, he said he saw people running down the street, and so he and his family began to run in the same direction. He ducked into a coffee shop and, after regrouping with his whole family, fled to a neighbor's house for safety along with a large group of other children and parents. Maggie Schmieder, 40, attended Monday's parade with family and friends. She described the moments after the shooting more as "chaotic calm" than terror or panic. "People weren't like sprinting or diving down," she said. "It was like there was this confusion, but people automatically started going." — CNN