Police in the US state of Illinois have captured 22-year-old Robert "Bobby" E. Crimo, suspected of being involved in a mass shooting at an Independence Day parade.
"We are considering him very dangerous," police said in a media release before he was taken into custody.
Six people are dead and at least 30 were taken to hospital after the attack at a July 4th parade in Highland Park, a city on the outskirts of Chicago.
Illinois police say Crimo, a person of interest in the shooting, was taken into custody during a traffic stop.
He initially fled police but then came to a stop and was arrested without incident.
During the shooting, many in the crowd took a moment to realise the horror unfolding - as slow moving police and fire trucks already had their sirens going as part of the parade. The noise masked the initial gunshots.
"I thought that it was the Navy that was saluting the flag with the rifles," said a witness, Alexander.
"But then when I saw people running, I picked up my son and started running."
He made his son hide in a nearby rubbish dumpster, before going back to find the rest of his family.
Another woman said she heard the gunfire stop - only to start after the shooter had re-loaded.
"People screaming and running. It was just really traumatising and scary," she said.
The emergency service crews taking part soon became the first responders on scene, as families fled to escape the shots - which police later said came from a nearby rooftop.
President Biden has released a statement saying he and the first lady are "shocked by the senseless gun violence" perpetrated on Independence Day.
Congress recently passed its biggest set of gun reforms in decades - expanded background checks and providing state grants to allow "red-flag" laws.
"There is much more work to do, and I’m not going to give up fighting the epidemic of gun violence," he said.