A man who was arrested near a Republican National Convention security zone Monday was concealing a firearm in a "tactical" backpack, police said.
The arrest took place about 1 p.m. on the 1200 block of North 11th Street, the Milwaukee Police Department said in a statement. Police determined the 21-year-old man did not have a permit to carry a concealed weapon, the police department said.
The location of the arrest was about two blocks outside the vehicle screening perimeter of the convention, which started Monday.
Law enforcement spotted the man, whose identity authorities had not released as of Tuesday night, and determined he looked suspicious, police said.
"Police initially observed the suspect looking suspicious, wearing a ski mask and a large tactical backpack in the street," they said.
The "subject stop" was conducted by U.S. Capitol Police, Milwaukee police said. Capitol Police did not answer specific question about the arrest Tuesday and referred inquiries to Milwaukee authorities.
Get Tri-state area news delivered to your inbox. Sign up for NBC New York's News Headlines newsletter.
A Milwaukee County spokesperson who fielded an inquiry for the district attorney also referred questions to police.
U.S. & World
The police department did not answer a question Tuesday about the type of gun involved. “This is an ongoing investigation. This is the information available at this time," a police spokesperson said.
The case was under review by local prosecutors.
The arrest happened two days after former President Donald Trump was targeted in an assassination attempt at a campaign rally Saturday in Pennsylvania. He survived after, he said, his ear was shot.
On Tuesday, police from Columbus, Ohio, shot a man who they said was holding two knives and moving toward another man he was arguing with. The officers were in Milwaukee to help with convention security and had gathered about a mile from the convention’s venues.
This story first appeared on NBCNews.com. More from NBC News: