One person was arrested Tuesday evening in downtown St. Paul during a traveling protest by up to 150 people calling for prosecution of the police officer who fatally shot Philando Castile.

The protest began about 4 p.m. when about 50 people ran out to the painted median in the middle of Kellogg Boulevard, soon blocking traffic. The group then swelled to about 150 people who marched downtown on Wabasha Street, temporarily blocking some streets. They then gathered in Rice Park, marching, chanting and waving signs.

A little after 6 p.m., protesters marched to the Ramsey County Courthouse and held a brief die-in in the middle of Kellogg.

Soon after, about two dozen St. Paul police officers arrived and threatened arrests, calling the rally an unlawful assembly. One officer speaking over a loudspeaker said demonstrators could leave east on Kellogg through a line of officers armed with long batons and guns. About 30 Ramsey County sheriff's deputies arrived to block the westbound lane of Kellogg.

St. Paul police called out two demonstrators by name and told them they were under arrest, in addition to threatening arrests in general to the entire group. They then tightened their circle and arrested one man.

Demonstrators eventually made their way back to Rice Park as the officers returned to their vehicles. Jacob Ladda, a demonstrator who spoke to the group throughout the rally, said police have identified leaders within local organizations and are targeting them for arrest.

Police spokesman Sgt. Mike Ernster said the arrest was made by police when "it was safe to do so." The man who was arrested allegedly blocked traffic, touched vehicles and made verbal threats against drivers who refused to allow demonstrators to cross when the vehicle had the right of way, Ernster said.

"The rally was allowed to take the street," he said, "but in the end ... it comes down to public safety — pedestrian and motorist safety."

Castile was fatally shot by St. Anthony police officer Jeronimo Yanez during a July 7 traffic stop. His girlfriend, who live-streamed the shooting's aftermath on Facebook, said Castile, who was armed and had a valid permit to carry, was reaching for his driver's license when he was shot.

Protesters have called for Yanez's criminal prosecution.

Ramsey County attorney spokesman Dennis Gerhardstein said his office has not been presented with the case for charging consideration, and has not been provided a timeline of when that might happen.

County Attorney John Choi hasn't decided yet whether he'll ask a grand jury to review the case for possible charges, or whether he'll make that decision himself, Gerhardstein said.

Chao Xiong • 612-270-4708