It is the responsibility of the security officer to ensure that properties and lives of people are protected and as well the security officer involved which entails the use of weapons as well.
Being a security officer you are admonished to trained on how to use weapons in the aspects of the usage of guns against the enemy.
it be an error for a security officer to use weapon when it entails killing the innocent citizens, especially citizens that did not fall victims or go against the constitution of the country.
With the understanding that it's job is not an easy one, he ought to do th job with diligent and carefulness so as to protect the live and the property of the nation with the fear of God dwelling in him.
As a security officer your weapn should be registered or licensed by the government, which implies that you have full control of it and you have signed to use it to protect the lives and properties of the nation to ensure that the enemy do not have control over the territory.
Defending oneself is not regarded as a sin