One 19-year-old student who was preparing to walk in the parade as shots rang out is detailing his personal ordeal.
Jack Barber, 19, is from Northbrook, Illinois — a small town about 15 minutes away from Highland Park, an affluent Chicago suburb. A student at UCLA, Barber was home for the summer and preparing to walk in the annual 4th of July parade on behalf of a local politician running for Congress.
"We were near the back of the parade, lined up getting ready to start," Barber told TODAY Parents. "As we were doing that, we just heard what sounded like a firecracker pop. Then we saw people running in every direction. At first we were a little confused — we didn't know whether it was a race of some kind or someone was trying to get away from the firecracker, maybe overreacting."
Seconds later, Barber realized he wasn't hearing fireworks — it was gunfire.
"We started running away," he added. "We probably ran about a half-mile into this neighborhood where a nice woman and her husband let us into her house, just to find cover and figure out what is going on."
Once safely inside, Barber says he was inundated with rumors: There was a shooting at a pancake house, he was first told, which turned out to be false.
"I heard someone was on a roof," he added. "That ended up being true."
The suspected shooter reportedly positioned himself on the roof of a business on the parade route before firing into the crowd of spectators, using what authorities described as a "high-powered rifle."
"We stayed (at the house) for a while, because we still felt unsafe," Barber said. "The woman was nice enough to drive us to a secondary location in Highland Park, where we stayed for a while. Later, one of my co-intern's parents came and picked us up and drove us home."
After an hours-long manhunt and brief police chase, a 22-year-old "person of interest" was apprehended without incident, but has not yet been charged.
'It so easily could have been me'
Barber says that as a student in the United States, he can’t count how many active shooter drills he has experienced over the years.
"It's absolutely sad and terrifying that I haven't really thought about how many times I've had to prepare for an active shooter," he explained. Regardless of those drills, Barber says nothing could have prepared him for the reality of a mass shooting.
"People were just dumbfounded. Even the first 10-15 seconds after we heard gunshots, we just stood around and watched," he said. "It wasn't like there was someone just in the middle of the street — it was very discreet. It wasn't until people saw people in pools of blood...it was...it was hard to really comprehend."
As some bystanders — many of whom were grandparents and parents with small children — stood in shock, others began to scream and run, Barber says. He heard a father shout at his family, "Get in the car, we're going now!" and decided he needed to leave, too.
"At first, we thought we didn't have to go far," he explained. Barber still thought people were just running away from fireworks.
"I thought we would be fine standing a couple hundred feet away. Then we realized," he added, his voice trailing off, "and we kept going. It's hard to recall — it was just mass confusion."
Now that Barber knows what happened, he says he can't stop thinking about how close he was to the carnage.
"It so easily could have been me," he said. Initially, Barber and his group were supposed to be positioned higher in the parade lineup. A last minute-change pushed them further back in line and, in the end, further away from the shooter's position.
"If the shooter would have waited another 5 minutes, I would have been right there."
'I don't feel safe'
As soon as he was safe, Barber said he called his mother.
"She was obviously very worried," he said. "A lot of my family members wanted to make sure I was OK. There was definitely a lot of relief, at least on my family's behalf."
Barber doesn't feel relieved, though, even though he's now home with his family.
"I don't feel safe," he explained. "I mean, I was sitting in my kitchen and I heard my dad moving a trash can or something. I heard the same noise, you know, with the shots. I'm standing in my own basement, worried that someone can come in the house.
"I think eventually, I don't know about 'be OK,'' he added. "But I'll probably get more comfortable just with time, hopefully."
"It can be really easy to ignore — it's a lot less personal when it's not your neighborhood or the neighborhood of people you know," he said. "It never really crossed my mind — we were just sitting at a parade. I was thinking about, you know, what I was going to have for lunch.
"The Fourth of July, it's supposed to be a happy celebration of our country," he added. "I think (the shooting) is definitely a metaphor for the way our country has been going recently."