The Metro Transit Police Department opened an internal investigation Sunday after a video shared on social media showed an officer shoving a man and using a Taser on him during an incident at the U Street station Saturday.

In the video, the man appears to be speaking with officers, who are talking to some juveniles, when another officer walks up and grabs him. Moments later, the officer can be seen shoving the man, drawing his Taser and firing.

“According to the officer’s statement, the subject took an aggressive stance with a balled fist and began to approach the officer appearing to be readying for a fight,” Metro spokesman Ron Holzer said in an email. Transit police arrested the man on a charge of assault on a police officer and obstruction of justice, Holzer said.

Videos posted online do not appear to show the man either balling his fist or assaulting the officer.

“It felt really gratuitous, even at the time,” said Kegan Queen, who captured video at the scene with his phone. “The man was obviously not hurting anyone. It felt really extreme.”

Police on Sunday refused to identify either the officer or the man who was arrested.

“MTPD opened the investigation today, and it will review all available facts and evidence, including witness statements and videos posted on social media,” Holzer said. “Because the investigation is active, we are unable to offer additional comment at this time.”

Queen was on his way home from work when he came upon the scene. He said he saw officers detain a youth, who had been in the station with a group of friends.

“The group took off,” Queen said. Officers “arrested the first kid and had him held down on the ground next to the Metro tracks when one of his friends came over and he was upset, so they arrested his upset friend as well.”

Chemere Jones, who said she had just finished apartment hunting and was heading to meet a friend, arrived at the scene about the same time.

“I get off the train, and I see two transit police officers with their hands on one little African American boy,” Jones said. “His hands were behind his back, and one of the transit officers had his knee in between the middle of his shoulder blades.”

Jones also began taking video. By the time her video begins, one of the boys is handcuffed, seated on a concrete Metro station bench, with two officers standing beside him. The man who would later be arrested can be seen standing on the opposite side of the concrete bench, talking with the officers. Jones and Queen said the man was trying to advocate for the boys.

Holzer, the Metro spokesman, said officers had arrived at the station around 5:42 p.m. “for a report of disorderly juveniles threatening Metro riders with sticks.”

Holzer said “witnesses pointed out a group of juveniles and stated they had been threatening riders with fireworks. Units contacted the group of juveniles and two of the juveniles attempted to flee.”

“While attempting to detain the juveniles the complaining witness left the scene. … No fireworks were located,” Holzer said.

On Jones’s video, she can be heard trying to calm another boy.

“I just want to make sure that you all are all right,” she says. “Because I see them looking at you all, and what I’m not about to do is have none of you all get hurt right now, all right?”

U street Cardozo Police are ridiculous. These were children.

Posted by Che'mere Jones on Saturday, June 22, 2019

Seconds later, an officer with a “Police K-9” vest walks into the video frame and immediately appears to put his hands on the man speaking with the officers from the other side of the bench.

As the man and officer exchange words, the man can be see holding his hands out on either side of him, open palmed, and taking a step toward the officer. The officer shoves the man in the chest, sending him backward. The officer draws his Taser, and less than 20 seconds after he first approached the man, the video shows the officer firing his Taser, as the man tries to wriggle away.

“He’s down! Leave him alone!” Jones can be heard yelling.

Melissa Laws said Sunday that she is the mother of one of the 13-year-old boys whom police detained. She arrived at the scene after getting a call from an officer.

“They said, ‘We want to speak with you before you see your son,’ ” said Laws, who is program director at the Shaw Community Center. “I said, ‘Absolutely not. My son is 13 years old. I want to see him.’ ”

Officers allowed her to see her son, and they soon let both boys go.

Laws said she wants to find the man who intervened on her son’s behalf.

“I would like to thank him for what he did for the boys,” she said. “He’s a hero. If he had not done that, it could have been worse.”