A bullet smashes through a glass of milk. Moments later, another blasts through a bottle of ketchup, then a third shatters a watermelon.

These images appear on a screen in front of a room full of young people, half way through a busy morning at school.

Then a boy’s head flashes up, and the pupils cover their faces with their hands. “No!” a few whisper.

“‘You want to see this?’, asks PC Rory Romani, who has the undivided attention of his audience. No-one did.

Hard-hitting, disturbing, horrific, and sad, Romani’s hour-long presentation to pupils at Bradford Academy, on gun and knife crime, taps into a whole range of emotions.

Called Operation Mineral, it forms a vital part of West Yorkshire Police’s anti-gun campaign Operation Quartz.

Using facts, figures and real-life cases, PC Romani tells the pupils about the implications of not only owning and using a weapon, but harbouring one for someone else.

“You can have situations in which older people pass them down to younger ones – people in your age group,” he tells the students.

“As police officers we know this happens, so we will always search younger men in a group first, and girls.

“Don’t listen when people say ‘the police will not search you’, because we will. Don’t listen when they say ‘the police won’t search girls’, because we will – we just do it differently.”

He cites an example – one of many – involving a diligent girl who did well at school and college, but lost her career prospects after her boyfriend stored a weapon at their home.

“She didn’t use it, but she knew it was there. You can’t get away with saying you are not involved – because you are,” said PC Romani, an army cadet officer who effortlessly commands the attention of a room.

He speaks of how firearms officers have a fraction of a second to respond to incidents involving weapons – having to decide whether a gun is real or not – and flicks through up a series of images to allow the children to do the same. It is not easy.

The success of cases brought under the Proceeds of Crime Act are highlighted – “If we can prove it, we will take it” – as well as the penalties of weapon-related crime.

He moves on to computer games. He tells pupils “They affect how we think.”

“Who plays Call of Duty: Black Ops 2?” At least a dozen hands go up. “That’s an 18. Why are young kids playing it? He adds: “It is vital to understand the difference between game play and reality.”

A firearms officer for eight years, PC Romani – who also speaks to college and university students – became involved with school presentations after his daughter made a suggestion.

“She said they had sat through a talk at school about firearms which had been really dull, and wondered why I didn’t do them.”

Last year he travelled to Venezuela, after being invited by the government to give a presentation and visit schools in the capital Caracas.

“We were seen as one of the best anti-weapons campaigns in the country, and it was great to be asked.”

Despite his tough exterior, he speaks from the heart. “I live in Bradford, I’ve got children here – I want it to be safe for everyone.”

As the talk comes to a close, and the parents of Liverpool schoolboy Rhys Jones speak movingly about their son, you could hear a pin drop. It is clear the message has hit home.

Pupils Natalia Orackova, Christian Laja, Chloe Barnes, Olivia Rowe and Nathan Wilford, all 13, found it shocking but interesting.

“It makes you really think,” says Christian, while Chloe adds: “There are parts that are gruesome, but we need to know about it.”

At Bradford Academy he is supported by schools police officer PC James Czornowol, and staff.

Vice principal at Bradford Academy Tehmina Hashmi sees the presentation as part of a wider package of work with young people, “in particular with Year 9 pupils who have the potential to become involved in unsafe behaviours.”

She adds: “To have a real person speaking to them about these issues is very powerful.”

Head of Year 9 Jason Lee says: “PC Romani does a great job – you can see that in the reaction of the pupils. This helps not only the school but the community.”

Adds PC Romani: “After one session, a child came up to me and said, ‘You probably saved my life’.”