A 24-year-old woman died on Saturday after she and another woman were hit by a car on a closed highway in Seattle while protesting against police brutality, authorities said.

Summer Taylor, who was from the city, died in the evening at Harborview Medical Centre, hospital spokeswoman Susan Gregg said.

Taylor and Diaz Love, 32, of Portland, Oregon, were hit when the vehicle barrelled through a panicking crowd of protesters on Interstate 5 early on Saturday morning, officials said.

Ms Love is in a serious condition in the intensive care unit at Harborview, Ms Gregg said.

Dawit Kelete, of Seattle, drove the car around vehicles that were blocking the motorway and sped into the crowd at about 1.40am, a police report released by the Washington State Patrol said.

Video taken at the scene by protesters showed people shouting “Car! Car!” before fleeing the road.

Ms Love was filming the protest in a nearly two-hour Facebook livestream captioned “Black Femme March takes I-5” when the video ended abruptly; with about 15 seconds left, shouts of “Car!” can be heard as the camera starts to shake before screeching tyres and the sound of the impact are heard.

A graphic video posted on social media showed the white Jaguar racing towards a group of protesters who are standing behind several parked cars, set up for protection. The car swerves around the other vehicles and slams into the two women, sending them flying into the air.

The driver, who was alone, fled the scene after hitting the protesters, Trooper Chase Van Cleave told The Associated Press. One of the demonstrators got in a car and chased the driver for about a mile. The protester was able to stop him by pulling his car in front of the Jaguar, Mr Van Cleave said.

Troopers arrived, and the driver was put in custody, Washington State Patrol Captain Ron Mead said.

Mr Kelete was described by officers as reserved and sullen when he was arrested, court documents said. He also asked whether the pedestrians were OK, the documents say.

Mr Kelete was detained at the King County Correctional Facility on Saturday morning on two counts of vehicular assault. Bail was denied.

A judge found probable cause to hold Mr Kelete on an investigation of vehicular assault. He faces a second court hearing on Monday at which the judge will determine whether he can be released on bail, court documents said.

Officials were trying to determine the motive as well as where he got on to the interstate, which had been closed by the state patrol for more than an hour before the women were hit. Capt Mead said they suspect Mr Kelete drove the wrong way on a ramp. Trooper Rick Johnson said the driver went through a barrier that closed the freeway before striking the women.

Troopers did not know whether it was a targeted attack, but impairment was not considered a factor, Capt Mead said.

Mr Kelete has a Seattle address. He is listed in public records as a student who attended Washington State University between 2011 and 2017 majoring in business and commerce.

The Washington State Patrol said on Sunday evening that, going forwards, it would not allow protesters to enter the freeway and would arrest pedestrians who did so.

Seattle has been the site of prolonged unrest since the May 25 police killing of George Floyd in Minneapolis, which sparked nationwide protests. Dozens of people were arrested last week in connection with protests as demonstrations continue.

Authorities cleared a group of protesters from Capitol Hill, Washington, DC, on Wednesday morning.

Protesters had shut the interstate for 19 days in a row, Capt Mead said at a press conference.

The State Patrol responded by closing sections of the interstate to keep drivers and demonstrators safe.

“In a time that requires care and flexibility, we are exercising the safest means possible to avoid injuries or worse to motorists, protesters, WSDOT personnel and our troopers by closing the roadway and separating protesters from vehicular traffic,” Chief John Batiste said in a statement on June 27, responding to complaints about the road closures.

Capt Mead emphasised that the freeway was “simply not a safe place” for pedestrians, and said he hoped protesters would cease unlawful behaviour in blocking the motorway.

“My hope is, as a result of this tragedy, protesters will reconsider their desire to be on the interstate because I cannot guarantee their safety, plain and simple,” Capt Mead said.

Seattle Mayor Jenny Durkan said the city stands beside the friends and family of the victims.

“No one should risk their life for demanding better from our city, state and country,” Ms Durkan said on Twitter.

Protesters were on the freeway for more than an hour before the car drove around the blockade at about 1.36am, Capt Mead said.

The state patrol tweeted two pictures of the driver’s car with significant damage to its bumper and windshield.