An unpermitted skateboarding event near San Francisco's Dolores Park Tuesday night escalated into an angry confrontation with police after a skateboarder and a San Francisco police officer collided.
The incident has led to allegations online from some witnesses who say the SFPD officer deliberately blocked the skateboarder on a downhill run, causing a crash that injured both the skateboarder and the officer.
Officer Robert Rueca said Wednesday morning that police are looking into those allegations and studying videos posted on social media of the incident and its aftermath.
"The matter is under investigation," Rueca said.
Police were first called to the park around 7 p.m. on a report of activity in the area of 19th and Dolores streets.
More officers were called out to the scene after police assessed the size of the crowd that had gathered for an unpermitted skateboarding event described online as "The Fastest Hill Bomb Contest" or "The Hill Bomb."
Videos show police cars blocking the street in some areas and skateboarders skating around them or using the sidewalks instead in some instances.
The event turned uglier after a skateboarder on a high-speed downhill run collided with an officer as he skated toward a gap in police cars.
Several witnesses posted videos after the event stating the officer had pushed or deliberately bumped the skateboarder, who fell and was injured.
Twitter user Joel Hamill posted a video of the incident with the statement "#sfpolice purposely push skateboarder into car causing serious injury."
Instagram user "swarmlife" also posted a video of the same incident from another angle and stated "Cop just caused a kid to eat sh**."
Police say they were trying to shut down a dangerous event. Skaters say police overreacted. Some people in the neighborhood say the fun turned dangerous when the crowd made it difficult for medics to get to a patient.
Fire crews had to wash blood off the street after skateboarders wiped out on the pavement.
Brother Damien Joseph of the San Damiano Friary said people called him outside when Thrasher magazine editor Jake Phelps smacked his head on the street. Joseph said the crowd turned on police as they tried to help Phelps.
"People were upset, crowding around him, refusing police direction to get out of the way so medics could get through," Joseph said.
A hospital spokesperson said Phelps was in fair condition Wednesday night.
Rueca said police attempted to provide medical aid to anoher injured skateboarder, but he refused assistance and officers were unable to interview him.
The officer in the collision was taken to a hospital with injuries not considered life-threatening, Rueca said.
During the ensuing confrontation, police say a crowd gathered and some people allegedly threw projectiles at officers and vandalized two police cars.
Police Chief Bill Scott updated the police commission Wednesday night.
"I found video disturbing," Scott said.
The chief said the deaprtment will review video from social media and body cameras.
"We are addressing the concerns I’ve heard about in terms of a collision with an officer," Scott said. "He was injured but is OK. We’ll take a look at it and investigate it."
A number of skateboarders fell during the incident, but most refused medical aid from police, Rueca said. One was transported to a hospital after a fall.
Rueca said police made several announcements asking the crowd to disperse, and tried to take a defensive line to contain it and protect both the skateboarders and vehicles and pedestrians in the area.
"We didn't have advance notice of this, this was an unpermitted event," Rueca said. "We were trying to make the situation safer and to keep it from getting worse."
The event, a race that was reportedly sponsored last year by Snack Skateboards and Skate Jawn, among others, took place last July with less conflict, according to witness and published accounts.
Videos posted online show skaters racing down Dolores Street with police standing by and even blocking traffic to facilitate.
Attempts to reach Snack Skateboards for comment this morning were unsuccessful.
Police remained on the scene until around 11 p.m. No arrests were made, Rueca said.
NBC Bay Area's Jean Elle contributed to this report.