An apparent burglar was found in our building on Shabbat afternoon. We stopped him and asked for identification which he didnt have. Were we allowed to call the police? As it turned out after the confrontation he pulled a knife and was on drugs. We did not know it at the time. Could we have immediatly called the police? He was a Jew in his fifties , a chiloni in a frum area.

Shalom, One is not allowed to break Shabbat (by telephoning) just in order to save one's money or property from being stolen. However, when there exists even the slightest chance that the burglar could become violent then one is obligated to do everything possible to save oneself or others (for example if caught in the act of theft he may pull a gun or knife and shoot etc). Therefore just finding a person in the building without identification does not seem to justify calling the police, unless one suspects he will likely go to another building and endanger lives there. If however he pulls a knife, or it is obvious from his actions that he may become violent (for example a person acting deranged because of drug use who may suddenly attack children), one should call the police. The burglar may also be detained, if this is possible without danger, until the police arrive (See Shmirat Shabbat KeHilchatah chap. 41, 25-29).