PORTLAND, Ore. – For the fourth straight night, anti-Trump protesters took to the streets of downtown Portland, and for the second straight night the protest turned into a melee.

Seventeen people were arrested throughout the night and one protester was shot on the Morrison Bridge early Saturday morning.

The protest began as a peaceful rally at City Hall at 5 p.m. before protesters split into what appeared to be three groups at around 7 p.m. There were at least 1,000 protesters and police said there were reports of vandalism and assault.

One group, organized by Portland's Resistance, stayed at the rally in City Hall. Despite pleas from police earlier in the day, some protesters began marching on Southwest 4th Avenue, only to be stopped by police, who advised the crowd to march on a facilitated northbound route.

Photos: Night 4 of Portland anti-Trump protests

A second group followed police orders and began marching north. Police said deviating from the route was not permitted.

"We will facilitate a march as long as it's on the streets we ask them to stay on," said Sgt. Pete Simpson of Portland police.

However, the group of protesters that headed north on Southwest 4th Avenue attempted strayed from the police route and attempted to cross the Burnside Bridge, only to be stopped by police. The group headed back downtown and at around 9 p.m. joined with the third group that stayed in a standoff with police on Southwest 4th Avenue.

Over the next couple hours, flash bangs and tear gas were used to disperse protesters, some of whom were throwing burning projectiles at police, on Southwest 4th Avenue. Police advised the crowd that their gathering was considered an unlawful assembly and they were subject to arrest. Still, the crowd continued to march elsewhere through downtown.

“It’s been a very aggressive crowd toward the officers," Simpson said.

Watch: Flash bangs deployed on Night 4 of Trump protest

Separate from the downtown area, a fourth group emerged at around 8:45 p.m. on the eastside and attempted to cross the Hawthorne Bridge westbound, only to be stopped by police. At that time, Interstate 5 was closed between the Marquam and Fremont bridges and Interstate 84 was closed at the junction with I-5.

In the early morning hours, a protester was shot on the Morrison Bridge. The victim is expected to survive.

More: Protester shot on Morrison Bridge

The City Hall rally was organized by Portland’s Resistance. Leader Greg McKelvey said the group would not march and the group stayed at City Hall while other protesters splintered into other groups.

“This group is going to remain peaceful and what we have tonight is beautiful," McKelvey said. "My group will hold this forum and just try to build community…and get people to mobilize our platform.”

During the rally, McKelvey called on Portland to acknowledge and rectify its racist past, and asked the crowd of supporters to be a model for the rest of the country.

"We have to make sure Portland can be a progressive model for the rest of the country," he said.