A pre-school teacher and her husband were shot in front of their two young children during the Highland Park rampage that left six people dead.
Zoe and Stephen Kolpack, her father and her brother-in-law were all injured when a gunman opened fire at a Fourth of July event in the Chicago suburb on Monday.
The family members are all said to be undergoing “various surgeries” in hospital, according to a fundraising page. They were among 38 people wounded in the latest US mass shooting.
Chicago Teachers Union shared a link to a GoFundMe page set up by Ms Kolpack’s friend Samantha Whitehead, asking people to give their support to the family. So far the page has raised more than $126,000 (£105,000).
It said: “Today at the Highland Park annual 4th of July parade my best friend, her dad, husband, and brother in law were all shot in front of their little kids (kids were unharmed).
“They are all in the hospital undergoing various surgeries, which will seriously impact these families financially.
“I do not want this to be another burden on them as they will have many obstacles to go through in the months ahead. Please donate whatever you can.”
Friends, parents of children taught by Ms Kolpack and strangers alike left generous donations and messages of support for the family.
One parent wrote: “Ms Kolpack is one of my son’s previous teachers, she is one of the nicest, most patient, sweetest people you will ever come across.”
A gunman perched on a rooftop opened fire on families waving flags and children riding bikes at the Fourth of July parade in the Chicago suburb on Monday.
Hours later, police announced they have arrested 22-year-old Robert E Crimo III, from the Highland Park area, following a brief chase.
Dozens of fired bullets sent hundreds of parade-goers fleeing, including some who were visibly bloodied.
Among the victims was grandfather Nicolas Toledo, in his 70s, who was visiting his family in Illinois from Mexico.
He was shot and died at the scene, his granddaughter, Xochil Toledo, told the Chicago Sun-Times.
Ms Toledo said her father tried to shield her grandfather and was shot in the arm. Her boyfriend was also shot in the back and taken to a nearby hospital by someone because they were unsure whether there would be enough ambulances for all the victims.
Roberto Velasco, Mexico’s director for North American affairs, said on Twitter that two Mexicans were also wounded.
Also killed was Jacki Sundheim, a lifelong congregant and "beloved" staff member at nearby North Shore Congregation Israel, which announced her death on its website.
NorthShore University Health Centre received 26 patients after the attack. All but one had gunshot wounds, said Dr Brigham Temple, medical director of emergency preparedness.
Their ages ranged from eight to 85, and Dr Temple estimated that four or five were children.
