Pittsburgh mayor has ‘serious concerns’ over arrest tactics

A crowd of protesters - carrying signs like 'abolish the police' marched to the home of Pittsburgh Mayor Bill Peduto over the weekend... outraged over the arrest of a protester at a demonstration.

Matthew Cartier was arrested on Saturday at a Black Lives Matter protest. A video cited by CBS News showed plainclothes officers putting Cartier into an unmarked van.

Police say he interfered with public safety.

But after the gathering of about 150 protesters outside his home, Mayor Peduto is now speaking out. He said he had 'serious concerns' over the tactics used on the protester.

Police said Cartier was arrested because he stepped in front of cars, tried to direct traffic and blocked an intersection used for hospitals and the University of Pittsburgh. He is now facing charges.

The arrest comes as protests against racism and police brutality have spread across the U.S. and in recent days have become violent.

Over the weekend, tensions flared as right wing demonstrators clashed with leftist counter protestors in multiple states, leading to fights and arrests.