The students might not be the ones who is doing the bullying but how are they involved? Is it by laughing at the victum being bulllied and watching it? Or is by not doing anthing when you see someone being bullied? How are they involved?
Bullying is a problem that has three sides - the bully, the victim, and the bystander. The person you are describing is the bystander. Bystanders can either be part of the problem by laugh and encouraging the bully to continue or part of the solution where he/she tries to help the victim.
I believe as adults we need to model doing what is right. If that means getting involved and sticking up for the victim, then do it. If it means we need to point out that sometimes our teasing or joking around can be hurtful, then say your sorry. Children learn best by example.
Students can be involved in many ways, directly or indirectly.
Instigating a problem and then removing themselves is one way, another would be directly pushing, picking or bringing harm to an individual or group.
Observing is not necessarily considered bullying, a student could be witness to an event without any connection whatsoever. Like being near a car accident, one driver may witness what had taken place from a side road and there is actual nothing they can do as they watch the event happen right before them, but they wouldn't leave the scene of the accident, you would stay and want to help if possible or be witness for authorities.
Laughing, well, it's not a joke or a laughing matter. As referenced to the car accident, you might witness the crash, but you wouldn't laugh. Laughing at a bully committing a violation against another would be as though you are encouraging and offering your support to the bully so, yes, I would say that is the same as a bully or at very least a sign of immaturity or developmental problem.
Hope this answers your question. Bullies are victims of insecurities and low self esteem and they feel empowered by distressing another who has their life "together". Its as though they feel that if they can make someone else feel poorly, then it makes them feel good. It is a mental disorder and a condition. It is everyone else's responsibility to identify these disturbed individuals and help them receive the care needed so they can perform in the society that we must live in. They are time bombs and if left untreated, devastating results can occur, such as the shootings, attacks and other crimes that we see on the evening news daily. The predator was a mentally disturbed individual that somewhere, someone did not identify and provide proper medical attention. We are all responsible at some level.