Videos from two D.C. police body-worn cameras made public Thursday show a police cruiser closely following a moped moments before the moped driver exited an alley in Northwest Washington and collided fatally with a van.

After the crash on Kennedy Street, an officer from the cruiser yelled “Karon,” indicating he had prior interactions with 20-year-old Karon Hylton, who died after the Oct. 23 crash in the Brightwood Park neighborhood.

D.C. Police Chief Peter Newsham said investigators are trying to determine whether the officers in the vehicle were chasing the moped, which could be a violation of rules prohibiting pursuits for traffic violations.

Authorities said the four officers in the vehicle have been put on leave with their police powers revoked as the investigation proceeds. They were part of a crime-suppression team targeting areas around Kennedy Street NW.

Police have said the officers were trying to conduct a traffic stop of Hylton, who was operating a rented Revel electric scooter, because he was driving it on the sidewalk and was not wearing a helmet.

Officials said they are seeking to determine whether the officers had another reason for trying to stop Hylton. Newsham said no contraband was found and no serious crimes had been reported in the area at the time.

Mayor Muriel E. Bowser (D) identified the officer who was driving as Terence Sutton, who joined the force in 2009. The other officers in the police vehicle were not identified. Sutton could not be reached for comment. A union representative did not respond to questions about the officers.

Hylton’s death has angered family members and his community, who contend that police had harassed him in the past and then chased Hylton to his death. The fatal crash has prompted three nights of demonstrations outside the 4th District police station on Georgia Avenue NW. The protests have sometimes been volatile, with more than a dozen officers injured and station windows broken Tuesday and Wednesday nights.

On Thursday evening, as it rained, a group of about 75 people gathered outside the police station. Among them was Hylton’s mother, Karen Hylton, who was seen swinging an aluminum baseball bat at police fencing. She shouted at bike patrol officers, with demonstrators also raising their voices at police. Three water bottles were thrown at the officers. Police units waited in reserve.

Charles Brown, Hylton’s father, earlier Thursday said that he watched the body-camera videos showing the events leading up to his son’s death but that he didn’t want to comment on them. He also didn’t yet want to say whether he thinks the officers involved should be disciplined or charged, but he had a general message for the police.

“What I want to say to every officer out there that says he’s a good officer, what I need them to do is check the other officers that are not good,” Brown said.

The video from Sutton’s body-worn camera begins shortly after the officers drive into the alley in the 700 block of Kennedy Street NW. About halfway along the alley, it appears that an officer turns off the vehicle’s emergency lights, but the cruiser still follows the moped at a close distance.

It also appears from the video that Sutton activates his camera as he gets out of the cruiser, after the moped and van collide. The video preceding that point is the two minutes of advance data that is automatically saved once a body-worn camera is activated. Audio is not recorded during that period.

D.C. also released a video from the officer in the passenger seat that shows more of the period before the crash. It did not include audio from within the cruiser.

Newsham said police must turn on their cameras as soon as they initiate a traffic stop, generally at the same time that they activate their emergency lights. Failing to do so, the chief said, “would be a very serious violation” that could lead to the firing of an officer. Newsham said the department is investigating at what point the officers activated their cameras.

D.C. Council Member Charles Allen (D-Ward 6), who chairs the council’s public safety committee, said that had the cameras been turned on earlier, audio would be available from the officers as they followed Hylton.

That, he said, would help in understanding why the officers were intent on stopping him. “I think at the end of the day it’s pretty clear this is not about someone not wearing a helmet,” Allen said, adding that he did not want to speculate on the possible motives of the officers.

Police said they also are trying to determine the path of the moped and the officers. A surveillance video from a private home, broadcast by WRC-TV, shows a moped traveling near Seventh and Kennedy streets NW followed by a police vehicle with its lights and siren on.

The video from the officer in the passenger seat shows the police cruiser turning from one street to another, with that officer pointing, apparently helping the driver to keep track of Hylton. At one point, the officers turn off the emergency lights, then turn them back on a few moments later.

Once the vehicle is in the alley, the emergency lights go off again, but the cruiser keeps going, and Hylton is struck a few seconds laterwhen he darts out onto Kennedy Street between parked vehicles. Officers administered first aid and called for an ambulance. One officer is heard on the video saying, “Man, he’s driving crazy.”

Dennis Jay Kenney, a professor at John Jay College of Criminal Justice and a former police officer in Florida who has written about police pursuits, said he saw evidence of a chase in the incident.

Kenney, who watched the videos made public by D.C. police, noted the extended time of the incident and the numerous turns made by the vehicles. He said he believes the officers were using the helmet infraction to stop Hylton to search or question him in other matters.

“It’s a minor infraction and you got a four-officer anti-crime team that is supposed to be out looking for major crime,” Kenney said. “It’s highly unlikely they’re working helmet violations.”

Andrew J. Scott III, the president of AJS Consulting, which advises on police issues, also said he thinks a pursuit is evident in the video. He noted that “the officer turns on his lights” as they turn onto several streets. “At one point he turns off the emergency lights, then turns them back on. They’re still going after this guy.”

Newsham said it is sometimes difficult to determine when a police officer’s attempt to pull over a vehicle becomes a pursuit. He said the officer “has to make a determination the person is fleeing.”

Newsham and Bowser offered sympathy to Hylton’s family. The mayor, however, warned the community that “we cannot channel that anger into violence.”

Crowds that gathered at the 4th District police station for two nights had demanded more details of the encounter. At times, protesters and police clashed, with protesters smashing windows and throwing bottles and fireworks at officers. Police sprayed chemical irritants.

Newsham said 14 officers were injured, with several of them hit by fireworks, one seriously enough to be admitted to a hospital. The union president said injuries include eye damage from lasers, eardrum injuries caused by exploding fireworks, and concussions from projectiles.

Police arrested eight people, with charges including destruction of property and assaults on police. There also was some damage done to businesses downtown and in Georgetown, though police said it was unclear whether those incidents were related to the Hylton demonstrations.

Authorities said they could not provide an account of injuries to demonstrators, though social media indicated many were injured.

Dana Hedgpeth, Keith L. Alexander, Emily Davies, Fenit Nirappil and Clarence Williams contributed to this report.