Suspect Robert E Crimo III was arrested hours after Monday's attack in the suburb of Highland Park, Illinois.

The 21-year-old had planned his attack for several weeks and is alleged to have climbed a fire escape ladder on to the roof of a business before firing more than 70 rounds at the crowd with a high-powered AR-15-style assault rifle.

Police said he had dressed in women's clothing to hide his facial tattoos, to blend in as he escaped the scene

Lake County State's Attorney Eric Rinehart said there will be dozens more charges laid against Crimo and, if convicted, he faces a life sentence without the possibility of parole.

In a statement released via Twitter Robert Crimo's parents said their hearts went out to the victims.

"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," they said. "Our hearts, thoughts, and prayers go out to everybody."

Among the dead were Nicholas Toledo, a grandfather from Mexico aged in his 70s who was celebrating Independence Day with his family at the parade, and Jacki Sundheim, a teacher at a nearby synagogue.

Lake County Major Crime Task Force spokesman Christopher Covelli said the suspect had been arrested after his vehicle was spotted, and officers at the scene found a second rifle in his car.

Officials said they did not know the motive for the shooting but did say that Crimo legally bought two high-powered rifles and three other weapons.

This was despite authorities being called to his home twice in 2019 after a family member said he had threatened "to kill everyone" there.

Mr Covelli said police had confiscated 16 knives, a dagger and a sword, but there had been no sign of any guns at the time.

The rifle used in the attack had been legally purchased in Illinois within the past year, Mr Covelli said.

Read more:
Fourth of July shooting suspect Robert Crimo's strange and violent online trail

It comes just weeks after 19 children and two teachers were shot dead at an elementary school in Uvalde, Texas, and 10 people were shot dead at a grocery store in Buffalo, New York.

There have been 15 shootings this year in which four or more people have been killed, according to a database maintained by The Associated Press, USA Today, and Northeastern University.