A two-year-old boy found bloodied and alone after the deadly shooting attack on a July 4 parade in a Chicago suburb has been orphaned by the tragedy.

On Tuesday (US time), friends and authorities confirmed that the toddler’s parents, Kevin McCarthy, 37, and Irina McCarthy, 35, were among seven people killed in the tragedy.

The boy, named Aiden, was reportedly rescued after a woman and her friends saw him pinned under his unconscious father, in the chaos after a sniper opened fire from a rooftop.

The woman, Lauren Silva, said she took Aiden back to her car, while her boyfriend and his son tried to help his father, who was bleeding. Ms Silva later told The New York Times that she was told that first responders were unable to stop Mr McCarthy’s bleeding and had covered him with a blanket.

Aiden was later returned to extended family members, according to a fundraising page.

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“He will have a long road ahead to heal,” said Irina Colon, who organised the GoFundMe page with the family’s permission, adding that his grandparents would care for Aiden.

The fund had raised more than $US1.2 million ($1.77 million) by Wednesday morning (Australian time).

Mr McCarthy was remembered as a “star employee” of Jaguar Gene Therapy with an “incredible work ethic.”

“Outside of work he was a very proud dad and devoted husband who adored his family,” company chief executive Joe Nolan wrote in an email.

“We will miss him tremendously.”

Ms McCarthy’s childhood friend, Angela Vella, described her as fun, personable and “somewhat of a tomboy” who still liked to dress up nicely.

“She definitely had her own style, which I always admired,” Ms Vella said.

Two-year-old Aiden’s tragic loss was confirmed as four others killed in the shooting were also identified. They were Katherine Goldstein, 64; Jacquelyn Sundheim, 63; Stephen Straus, 88; and Nicolas Toledo-Zaragoza, 78.

All were from the affluent town of Highland Park, where the shooting occurred, except for Mr Toledo-Zaragoza. He was visiting family in the city from Mexico.

Officials are yet to identify the seventh victim.

Thirty-nine people were taken to hospitals run by NorthShore University HealthSystem, ranging in age from 14 to in their 70s, said spokesman Jim Anthony. Nine remain hospitalised.

A 69-year-old man is in a critical condition with a gunshot wound.

Nine people were treated by Northwestern Medicine Lake Forest Hospital, six for gunshot wounds, three for falls, said spokesman Christopher King.

Four remain hospitalised, with their conditions ranging from good to fair.

Illinois authorities have charged 21-year old Robert E. Crimo III with seven counts of first-degree murder after the shooting.

If convicted, Crimo would face a maximum sentence of life in prison without the possibility of parole, Illinois state attorney Eric Reinhard said.

He said the first-degree charges were likely to be followed by dozens of additional indictments.

Crimo is due to appear in court on Wednesday. Mr Reinhard said he would ask that the suspect be held in custody without bail.

Authorities said Crimo had planned the attack for weeks and had come to the attention of authorities at least twice after reports he threatened suicide or harm to others.

They allege he fired more than 70 rounds from a rooftop at random onto people watching Monday’s Independence Day parade in Highland Park, Illinois. He made his getaway dressed in a disguise to blend in with the panic-stricken crowd, authorities said on Tuesday.

Crimo surrendered to police on Monday, hours after the attack.

Officials said they did not know the motive for the shooting in a neighbourhood with a large Jewish population. There was no immediate evidence of any anti-Semitic or racist basis.

The suspect used a high-powered rifle for the attack, similar to an AR-15, which he dropped at the scene.

He had a similar rifle in his mother’s car, which he was driving when taken into custody by police, and owned other guns at his home, all of which were bought legally in Illinois, officials said.

-with AAP