Police confiscated a collection of 16 knives and a sword in 2019 from the man suspected of carrying out the mass shooting near Chicago on Monday after he made threatening comments to family members.
The deputy chief of the Lake County Sherriff’s Office Christopher Covelli said police had been contacted by a family member in September 2019 that the suspect had knives and had said he was “going to kill everybody”.
He said police in Highland Park in Illinois had removed 16 knives, a dagger and a sword from the home, but there was no probable cause to arrest the suspect at that time.
He said the suspect in the mass shooting on Monday, who has been identified as 21-year-old Robert Crimo, did not have any guns at that time.
He also said that in April 2019 a person contacted Highland Park police to say that Mr Crimo had attempted suicide.
Deputy chief Covelli said police spoke with Mr Crimo and his parents at the time but did not pursue the matter further because it was being handled by health professionals.
Deputy chief Coveilli told a press conference that subsequently Mr Crimo had purchased five guns.
The new details came as authorities charged Mr Crimo with seven counts of first-degree murder over the deadly massacre. Announcing the charges in an evening press conference on Tuesday, the Lake County state’s attorney, Eric Reinhard, said that the community of Highland Park would “never be the same” and promised the charges were just “the first of many”.
Earlier, police said Mr Crimo had planned the shooting at the Fourth of July parade for several weeks.
Police maintained that the suspect had worn women’s clothes at the time of the shooting in the Highland Park suburb on Monday morning to disguise his appearance, including his facial tattoos.
Police said they had not yet identified any motive for the attack, and had no information that it was linked to either race or religion.
At a press briefing on Tuesday police maintained that Mr Crimo, had climbed up a fire escape ladder to the roof of a building and fired about 70 rounds from a high-powered rifle into the crowd attending the parade at Highland Park in Illinois.
Six people died in the attack on the Independence Day parade on Monday morning, and more than 30 were wounded. On Tuesday afternoon, authorities confirmed a seventh person had died in hospital.
A teacher at a Highland Park synagogue and a grandfather in his 70s who came from Mexico to visit his family were among those killed.
Deputy chief Covelli said that after the attack Mr Crimo left the scene and blended into the crowd. He said the suspect had walked to his mother’s house nearby and borrowed her car.
Mr Crimo, who is 21 years old (not 22, as authorities said on Monday), was detained by police on Monday night after a brief car chase.
Mr Covelli said Mr Crimo had bought the rifle used in the attack in Illinois and that it appeared to have been purchased legally. He said when Mr Crimo’s had been pulled over by police on Monday night after a public alert was issued, he had a second rifle in the vehicle.
He said other guns had been recovered from a residence. The attack appeared to have been “completely random”.
“We have no information to suggest at this point it was racially motivated, motivated by religion, or any other protected status,” he said.
He said investigators were reviewing videos posted online by Mr Crimo and had been “in discussions” with him while he was in police custody. “At this point,we have not developed a motive,” Mr Covelli said.
Highland Park is an affluent suburb of about 30,000 people, situated about 40km north of Chicago. Mr Covelli said more than 30 people who were injured in the attack had been taken to local hospitals.
Mr Crimo was a local rapper and police said they would be reviewing his music videos “to see what they reveal”. As a performer he used the name Awake the Rapper. The word “awake” was tattooed on his face.
One video featured a cartoon animation of a stick figure wearing what appeared to be tactical gear and shooting a rifle. A voice-over in the video said: “I need to leave now, I need to just do it. It is my destiny. Everything has led up to this; nothing can stop me, not even myself.”
The killings on Monday were the latest mass shooting in the US in recent weeks. In May 10 people died in an attack on a supermarket in Buffalo in New York state, while 19 children and two teachers were murdered after a man with an assault rifle attacked their school in Uvalde in Texas.
Earlier this month US president Joe Biden signed into law the first bipartisan gun-control reform legislation in more than 20 years, but critics maintained that it did not go far enough.