Six people were killed and more than two dozen injured after a gunman opened fire at a July 4th Independence Day parade near Chicago.
In the latest mass casualty shooting in the United States in recent months, police said the gunman fired randomly from a roof at people who were taking part and watching as the parade passed through Highland Park in Illinois.
More than 100 police officers and law enforcement official launched an immediate investigation and an “aggressive” manhunt for the suspected gunman.
Late on Monday, police identified a 22-year-old man as a person of interest in relation to the shooting. They said they were searching for Robert E Crimo, who is from the area. They said they considered him to be “armed and dangerous”.
Police were reported to be going door-to-door as they hunted for the gunman on Monday afternoon. Police snipers took up positions on buildings.
The suspect was described as being a white male, between 18-20 years old, of slight build and with black hair.
Local police commander Chris O’Neill said a weapon had been recovered at the scene.
Highland Park is an affluent suburb of about 30,000 people. It is situated along the Lake Michigan shore, about 40km north of Chicago.
Police said that shortly after 10am on Monday when about three-quarters of the parade in Highland Park had passed through the town they had received reports that a gunman opened fire.
Democratic congressman Brad Schneider, who was at the scene, said as soon as a the shots rang out “everyone scattered and ran”.
Chris Covelli, deputy chief of the Lake County sheriff’s office, said the attack “appears to be completely random”.
Mr Covelli said officials believed the gunman had used a high-powered rifle and had fired from a rooftop.
He said it seemed that both spectators and participants in the parade had been targeted by the gunman.
Police said officers assigned to work at the parade had run towards the gunfire but the gunman had ceased firing as they closed in.
Mr Covelli said “all indications are he was discreet and very difficult to see”.
He said six people had been killed in the attack, most at the scene and some in hospital. He said 24 people had been taken to various hospitals in the region. He said their conditions ranged from serious to critical.
US president Joe Biden said he was shocked by the “senseless gun violence that has yet again brought grief to an American community on this Independence Day”.
Mayor Nancy Rotering of Highland Park said: “On a day that we came together to celebrate community and freedom, we are instead mourning the loss, the tragic loss, of life, and struggling with the terror that was brought upon us.”
Illinois governor J B Pritzker said: “There are no words for the kind of monster who lies in wait and fires into a crowd of families with children celebrating a holiday with their community.”
“There are no words for the kind of evil that robs our neighbours of their hopes, their dreams, their futures.”