Five teenagers, including a 13-year-old girl, have been arrested after a mass brawl involving machetes broke out at a cinema.
Seven West Midlands Police officers were hurt while attempting to disperse the fighting at the Star City complex in Birmingham on Saturday evening.
The force said for those responding to the disorder "it may be the worst thing they have ever seen".
Police drew Tasers and used a dispersal order to clear about 100 youths.
Footage from inside the venue appears to show disorder breaking out and people on the floor screaming.
A girl aged 13, a girl and boy both aged 14, and a 19-year-old man were all held on suspicion of assaulting police. In addition, a boy aged 14 was held on suspicion of obstructing police.
All five were later arrested on suspicion of violent disorder but have now been released on bail with conditions which ban them leaving home at night and ban them from Star City and any cinema in the UK, police said.
A 14-year-old boy had also been arrested on suspicion of violent disorder after an image circulated on social media showing a number of youths, with one carrying a machete.
Asked if he was concerned about the ages of those involved, Ch Supt Steve Graham said: "It is concerning, there's no point pretending otherwise.
"That's why we've got plans in place, starting from first thing on Monday morning, where we'll be sending neighbourhood policing officers into schools around Birmingham to try and find out why."
Mr Graham added: "It's always hard to gauge these sorts of things - but what I will say is incidents like last night are rare.
"As for some officers who were there last night, it may be the worst thing they have ever seen."
The trouble "seemed to be focussed at the cinema" but "pockets of disorder" broke out around the whole complex for between 90 minutes and two hours, the force said.
Two machetes were seized and a knife was recovered from a roundabout nearby.
Since the disorder, the Vue cinema chain has pulled the gang film Blue Story from its 91 outlets in the UK and Ireland, a decision its director Rapman described as "truly unfortunate".
He said he sent his love to all those caught up in the trouble, adding: "It's truly unfortunate that a small group of people can ruin things for everybody. Blue Story is a film about love, not violence."
A Vue spokesman said: "We can confirm a decision was made to remove the film. The safety and welfare of our customers and staff is always our first priority."
Mr Graham said: "I understand there is a lot of speculation on social media and people are citing that film. At this stage we are not jumping to any conclusions. That will form part of our investigations as it carries on."
'Scariest moment of life'
Witness Choleigh McGuire described the brawl as "one of the scariest moments of [her] life", as she queued to watch the new Frozen film with her daughter.
"Armed police come, Tasers come, all of the people that were fighting ran off into the cinema, hiding. I am shaking," she said.
Another witness, Rachael Allison, said "a young boy was crying on the floor with his mother" as a number of people started fighting.
"The police told everyone to leave the cinema as they held Taser guns in their hands and started to bring in guard dogs."
The force was called to the complex, in Nechells, at about 17:30 GMT and cleared the area by 21:00. The officers hurt during the disorder suffered minor facial injuries.
Supt Ian Green said: "This was a major outbreak of trouble which left families who were just trying to enjoy a night out at the cinema understandably frightened.
"We worked quickly to move the crowds on, but were met with a very hostile response and officers had to draw Tasers to restore order.
"It's clear that some of those who went to Star City last night were intent on causing trouble."
He said the force's response was necessary to restore order as quickly as possible.
"We understand that families with young children will have been left upset by what they saw last night, but we urge people to appreciate that our aim last night was to protect the public and restore order, and that's what we achieved," he added.
Additional security is in place at the complex and police will be there on Sunday night.
Mr Graham added: "We know that Birmingham isn't unusual in this. Let's not pretend that knife crime or violence in the under 25s is rare or is just isolated around Birmingham.
"There are no short-term fixes to this, so we're prepared and we're in this for the long run and we're going to work with schools and other partners to prevent youth violence becoming an increasing problem."