Certain Male Sikhs carry ceremonial religious daggers normally secured shut by cloth, and wear them because it is in their religion to use the daggers, which were historically larger and unsecured, to defend OTHER religions right to believe what they believed and to defend themselves when attacked by weapons. The dagger, known as a Kirpan( https://en.wikipedia.org/wiki/Kirpan ) has become so ceremonial some are just a handle attached to a sheaf.
The Sikh who stabbed Henry Nowak was believed to be mentally unstable and was barred from his Sikh Temple because he, among other things carried a larger second dagger/Knife, which he had no right to carry, and was what he used to stab Henry Nowak.