(CNN) — Hours after gunfire interrupted the Highland Park, Illinois, July Fourth parade, killing six people and wounding dozens more, police apprehended the man they believe was responsible.

Robert “Bobby” E. Crimo III, 21, has yet to be formally charged in the shooting, which authorities said he allegedly carried out by climbing onto the rooftop of a nearby business and opening fire on the parade minutes after it started, sending parade-goers running for safety.

Investigators believe the suspect planned “this attack for several weeks,” Chris Covelli, spokesperson for the Lake County Major Crimes Task Force, said in a news conference Tuesday. The suspect dressed in women’s clothing to help conceal his identity, Covelli said, blended in with the crowds as they fled the area, and went to his mother’s house.

Law enforcement have yet to establish a motive, but Covelli said there has been no information to suggest the attack was “racially motivated, motivated by religion or any other protected status.” There is no indication anyone else was involved, Covelli said.

The suspect was taken into custody soon after police publicly identified him Monday as a “person of interest” who the FBI said was “being sought for his alleged involvement in the shooting of multiple individuals” at Highland Park’s Independence Day parade.

The suspect took his mother’s vehicle, and a member of the community saw him, Covelli said. That individual called 911 and North Chicago police conducted a traffic stop and took him into custody.

Police previously said Crimo was 22 years old, but on Tuesday, said he is actually 21.

Here’s what we know about him.

Follow live updates: Suspect in custody after deadly Illinois July Fourth parade shooting

He legally obtained the weapon used, mayor tells CNN

The suspect legally purchased the weapon he used in Monday’s shooting, Covelli said Tuesday, describing it as a “high-powered rifle” which shot high-velocity rounds. The weapon, which he described as “similar to an AR-15,” was purchased locally, Covelli said, within the Chicagoland area.

Investigators believe he fired more than 70 rounds over the course of the attack, Covelli said, and there is no indication the weapon was modified.

Crimo also legally purchased a second rifle found in his vehicle at the time he was apprehended, as well as other firearms recovered from his residence, which Covelli described as pistols.

Firearm evidence was found on the rooftop of a business near the shooting, Covelli said Monday, describing the gun as a “high-powered rifle.” At the time, authorities were working to trace the firearm to find out who purchased it and its origins, according to Bureau of Alcohol, Tobacco, Firearms and Explosives spokesperson Kim Nerheim.

The expedited trace of the firearm was “a major investigative lead,” Covelli said Tuesday, and helped identify the suspect along with witness statements and videos from the community.

A total of 39 patients were treated at four NorthShore University HealthSystem hospitals, according to spokesperson Jim Anthony, who said nine patients remained hospitalized in the system as of Tuesday afternoon. Four are in good condition, four are in stable condition, and one, a 69-year-old man, was in critical condition.

Eight of the nine patients suffered gunshot wounds, including the 69-year-old man, Anthony said.

Police in Highwood, Illinois — the suspect’s hometown, just outside Highland Park — had no prior crime-related interactions with Crimo, according to Highwood Police Chief Dave Wentz.

The only contact the department had with Crimo involved a noncriminal incident where Crimo was present when he was a juvenile, Wentz said.

“We literally have nothing on him,” Wentz said. “He was not potentially involved in anything.”

He posted violent imagery online

The suspected shooter posted music on several major streaming platforms under the pseudonym Awake the Rapper, and he apparently made and posted music videos online featuring ominous lyrics and animated scenes of gun violence.

In one video titled “Are you Awake,” a cartoon animation of a stick-figure shooter resembling the suspect’s appearance is seen wearing tactical gear and carrying out an attack with a rifle. Crimo, seen with multicolored hair and face tattoos, narrates, “I need to just do it. It is my destiny.”

In another video titled “Toy Soldier, a similar stick-figure resembling the suspect is depicted lying face down on the floor in a pool of his own blood, surrounded by police officers with their guns drawn.

Law enforcement is reviewing the videos posted online, Covelli said at Tuesday’s news conference, noting police had not previously been made aware of them. “We’ll look at them and see what they reveal.”

Several of the suspect’s online postings “reflected a plan and a desire to commit carnage for a long time in advance,” Mayor Rotering said in an interview with NBC’s Hoda Kotb on “Today.

“And it’s one of those things where you step back and you say, what happened? How did somebody become this angry and hateful,” she said, “to then take it out on innocent people who literally were just having a family day out?”

YouTube and Spotify removed content tied to the suspect from their platforms, the companies confirmed Tuesday. They declined to answer questions about whether the content had been flagged or previously reported for violations of their respective terms of service. The companies also declined to say precisely when they removed the suspect’s content.

CNN has also reached out to Apple Music, Amazon Music, Tidal and Pandora with similar questions, but the companies have not yet responded.

His uncle says he saw no warning signs

Highland Park Mayor Nancy Rotering knew the suspect years ago, when she was his Cub Scout pack leader, she said, telling CNN, “Many years ago, he was just a little boy, a quiet little boy that I knew.”

“It breaks my heart. I see this picture and through the tattoos, I see the little boy,” she said. “I don’t know what got him to this point.”

The suspect’s uncle, Paul A. Crimo, was “heartbroken” to learn his nephew was believed to be responsible for Monday’s shooting, telling CNN,” There were no signs that I saw that would make him do this.”

The suspect lived in an apartment behind a house in Highwood, Illinois, owned by his father, said Paul Crimo, who also lives at the house. He last saw his nephew Sunday evening, he said, sitting on a recliner in the house and looking on his computer.

“Everything was as normal,” he said.

To Paul Crimo’s knowledge, his nephew did not have a job, he told CNN, though he worked at Panera Bread before the Covid-19 pandemic. Paul Crimo said he had never seen the suspect engage in violence or concerning behavior. He didn’t know of his nephew’s political views, either, describing him as a “quiet” person.

“He’s usually on his own. He’s a lonely, quiet person. He keeps everything to himself.”

The suspect’s father and Paul Crimo’s brother, Robert Crimo Jr., previously ran for mayor, he said. “We are good people here, and to have this is devastating.”

“I’m so heartbroken for all the families who lost their lives,” Paul Crimo said.

What we know about the Highland Park shooting suspect