STORY: Fourth of July celebrations in a Chicago suburb turned deadly on Monday, when a gunman perched on a rooftop opened fire on families.
After a manhunt that lasted hours, police said they had a suspect in custody after 22-year-old Robert E. Crimo III surrendered to authorities.
The motive was not immediately clear.
In eyewitness video obtained by Reuters, gunfire rang out as crowds attended a parade on the main street of Highland Park.
At least six people were shot dead, and dozens more were injured, including children.
One man said he had to resort to drastic measures to protect his son.
"I put my son in a dumpster and he sat there with his dog and I went back to look for the rest of my family. I left them with someone there so that I can go back to get my phone and find the rest of my family because they ran away also. And it was just horrible."
Illinois's Governor J.B. Pritzker condemned the tragedy.
"I am furious because it does not have to be that way, and yet we as a nation, well, we continue allow this to happen. While we celebrate the Fourth of July just once a year, mass shootings have become a weekly, yes weekly tradition.”
And in Washington D.C., U.S. President Joe Biden held a moment of silence for the victims.
"Each day we are reminded that there is nothing guaranteed about our democracy. Nothing guaranteed about our way of life. We have to fight for it, defend it, and earn it by voting."
Just hours after the shooting in Highland Park, officials and media said two Philadelphia police offers were shot as thousands of people celebrated a Fourth of July concert and fireworks show.
The shooting comes with gun violence fresh on the minds of many Americans.
In May, nearly 20 school children were killed at an elementary school in Uvalde, Texas, a little over a week after ten others were shot dead at a grocery store in Buffalo, New York.
Biden signed bipartisan legislation on gun reform into law last month, but said on Monday that much more still needed to be done.