Hundreds of Black Lives Matter protesters marched across the George Washington Bridge on Friday night, temporarily shutting down the ramp to upper level to vehicle traffic.
The march was promoted on social media but took drivers by surprise. There were major backups in both directions of the span for about an hour.
Demonstrators then marched to the 34th Precinct in Washington Heights where tensions escalated between police and protesters.
Officers rushed to set up barricades and several violent clashes were caught on camera. At least six people were arrested at the precinct, a police spokesperson said.
"There was no hostility towards the police. The police became hostile. There were tons of police in riot gear, but there were no riots happening here," said Hawk Newsome, chair of Black Lives Matter's Greater New York chapter.
Organizers say they want lawmakers to pass The Breathe Act. Under the bill, federal money and resources for police departments would be reallocated to help minority communities come up with alternative public safety measures.