A teacher who intervened in a playground altercation in which two staff members and a pupil were stabbed does not consider himself a hero, his brother has said. Police are continuing to investigate the incident at Ysgol Dyffryn Aman in Carmarthenshire, south-west Wales. A teenage girl has been arrested on suspicion of attempted murder. It has emerged that one of the teachers has neck injuries. Dyfed-Powys police said none of the wounds were life-threatening and all three people who were hurt had been discharged from hospital. The force said a knife had been recovered. A second teenager has been arrested in the area after allegedly making threats that alluded to the attacks. Police said the alleged threats involved a firearm and led to officers recovering a BB gun from an address in Cross Hands, a village about five miles from Ysgol Dyffryn Aman. Supt Ross Evans said: “We would like to thank the many members of the public who reported concerns around messages they had seen online. This allowed us to take swift action in executing a warrant and arresting a suspect. “While this investigation is being run separately to our inquiries into the major incident at Ysgol Dyffryn Aman, our officers will be seeking to establish both the credibility of the threats, and whether there was any connection between the alleged offences. Darrel Campbell, a teacher who has been at the school for 40 years, stepped in during the incident on Wednesday morning. His brother, Cefin Campbell, a member of the Welsh Senedd, told the Guardian: “He was one of the first teachers to arrive at the scene, there was a commotion going on, a lot of screaming and shouting. He instinctively dealt with the situation. “He had to deal with a very, very challenging situation. He doesn’t consider himself a hero at all. He acted instinctively; he thought it was the right thing to do. You know when you’re in that situation, you just make a quick judgment and you take action. “He’s been a teacher there for 40 years. He’s never seen an incident that has come close to this ever before. You get fights at the school yard, I mean that happened when I was in school, but nothing involving weapons.” One of the teachers injured is the deputy head, Fiona Elias. Campbell said: “We’ve known her for years. She’s a fabulous teacher, lovely personality, and it’s such a shame that this has happened. We obviously wish her well and it will take time for her not only to recover from the physical injuries but the emotional and psychological effect this has had on her.” The other teacher injured is Liz Hopkin. Campbell said: “She had injuries around her neck area, so that is obviously a matter of great concern. When you think about a knife around the neck area, if it had caught one of the main arteries we could have been talking about a fatality.” The school was locked down after the incident. The headteacher, James Durbridge, said he was proud of the students’ response. In a statement posted on the school website, he said: “I wish to commend all staff and pupils for their calm and mature response during today’s lockdown. We are proud to have witnessed pupils embodying the school’s core values while supporting their peers and staff.” Ysgol Dyffryn Aman remained closed on Thursday to allow police to carry out investigations. Darren Price, the leader of Carmarthenshire county council, praised the school’s response to the incident and said lessons would be moved online and wellbeing support would be available for pupils, parents and staff.