Greater Manchester police (GMP) have launched an internal investigation after a teenager said an officer throttled him after shaking his head at them following a protest. A video of the incident was filmed by an 18-year-old student, who said she was thrown to the floor by two officers in an attempt to prevent her filming. The students, who have asked not to be named, say a small group of them were walking home after the protest in Manchester city centre on Saturday evening when they passed a police van parked outside the Midland Hotel. The young man, also 18, shook his head in its direction and continued walking but was approached by an officer, who said: “Are you shaking your head at me, you little shit?” and threw him against the van. The video shows the student flanked by two officers against the van, while a third places his hands around his throat. He says he nearly passed out as the officer kept squeezing his throat. “I genuinely thought he wanted to kill me. That’s all I could like read from his body language and his eyes and his facial expressions – he just kept squeezing,” he said. The video appears to show another officer tapping his colleague’s arms as they were around the teenager’s throat, possibly in an attempt to intervene. The female student said when the police realised she was filming, an officer pushed her over. “And as I was falling, and the other police officer took his hand off [my friend] and grabbed me and pushed me down to the floor,” she said. The male student was taken to another police van across the street, searched and detained. He said he was not sure whether he was ever formally arrested, and was driven a short distance away and released outside a McDonald’s. Before getting out, he asked for the badge number of the officer who he said assaulted him. In response, he said he was asked if he wanted to spend a night in the cell. At that point, he said: “I just wanted to go, I didn’t want to be in their hands, it’s not safe.” Simon Pook, a solicitor who was monitoring the protest as an independent legal observer, confirmed the students’ accounts. Describing the scene as an “outburst of quite volatile aggression” towards a group of young people, he said that he did not see a risk that would justify the aggressive policing. Pook said the officers performed a “rear stack” arrest, where hands are placed behind the back in handcuffs, normally used to detain people perceived as violent or aggressive. Pook said the attitudes of the officers, who were from GMP’s tactical aid unit and included a sergeant on the scene, stood in contrast to the policing of the demonstration itself, during which “they stood back, they monitored and they facilitated protest”. Thousands marched through the city centre to protest against violence against women and the proposed police and crime bill. There were no other arrests. The young woman, who has faced abuse on social media since posting the video, says the incident has left her feeling shocked. “I actually have no issues with the police … I think we need them to feel safe, but now I do not feel safe any more. I did nothing. I was just videoing and they shoved me to the floor and laughed in my face afterwards,” she said. “I am a white girl, my friend is a white boy … I can’t imagine what it would be like for other people who aren’t as privileged as us.” In a statement, GMP said an 18-year-old man was detained for breach of the peace on Saturday and was later de-arrested. “Following a public complaint in regards to this arrest, the incident has been referred to GMP’s professional standards branch for assessment,” it said.