About 150 people took part, many of them wearing masks.

PORTLAND — A chanting crowd of protesters angry over recent police-involved shootings marched through downtown Portland on Monday evening.

The Oregonian reports that about 150 people took part, many of them wearing masks. By 8 p.m., the newspaper says police had taken at least four people into custody. Among the demonstrators' chants: "When cops attack, stand up, fight back."

Police used bicycle officers and officers on horseback in an effort to keep the marchers on sidewalks as they followed a rectangular route past the federal courthouse, the justice center and the federal building. At one point, a window was broken in a Bank of America office.

The protest is just the latest of several sparked by two recent police shootings.

On Jan. 29, a police officer shot and killed an unarmed man, Aaron Campbell, in what began as a welfare check.

On March 22, an officer fatally shot Jack Dale Collins, a homeless man who reportedly had advanced on the officer with a knife.