A security system comprising: a sensor (104,106,108) configured to detect a presence of one or more persons in an environment; an alarm configured to generate an alarm signal upon detecting a trigger event by the sensor when the security system is in an armed mode; a user device configured to receive from a processor a first notification for notifying at least one of the one or more persons to set the security system in the armed mode in response to a determination that a last one of the one or more persons is leaving the environment; and the processor, communicably coupled to the sensor, the alarm and the user device, the processor configured to: determine whether the last one of the one or more persons is leaving the environment, wait for a response from the user device within a finite time duration after notifying the at least one of the one or more persons to set the security system in the armed mode, the response being from the at least one of the one or more persons to set the security system to the armed mode, and set the security system in a notify mode if the response is not received by the processor from the user device within the finite time duration after notifying the at least one of the one or more persons to set the security system in the armed mode, wherein in the notify mode, upon detecting the trigger event by the sensor, the alarm does not generate the alarm signal, and the processor transmits a second notification to one or more mobile devices of the one or more persons indicating that the trigger event has occurred. a sensor (104,106,108) configured to detect a presence of one or more persons in an environment; an alarm configured to generate an alarm signal upon detecting a trigger event by the sensor when the security system is in an armed mode; a user device configured to receive from a processor a first notification for notifying at least one of the one or more persons to set the security system in the armed mode in response to a determination that a last one of the one or more persons is leaving the environment; and the processor, communicably coupled to the sensor, the alarm and the user device, the processor configured to: determine whether the last one of the one or more persons is leaving the environment, wait for a response from the user device within a finite time duration after notifying the at least one of the one or more persons to set the security system in the armed mode, the response being from the at least one of the one or more persons to set the security system to the armed mode, and set the security system in a notify mode if the response is not received by the processor from the user device within the finite time duration after notifying the at least one of the one or more persons to set the security system in the armed mode, wherein in the notify mode, upon detecting the trigger event by the sensor, the alarm does not generate the alarm signal, and the processor transmits a second notification to one or more mobile devices of the one or more persons indicating that the trigger event has occurred. determine whether the last one of the one or more persons is leaving the environment, wait for a response from the user device within a finite time duration after notifying the at least one of the one or more persons to set the security system in the armed mode, the response being from the at least one of the one or more persons to set the security system to the armed mode, and set the security system in a notify mode if the response is not received by the processor from the user device within the finite time duration after notifying the at least one of the one or more persons to set the security system in the armed mode, wherein in the notify mode, upon detecting the trigger event by the sensor, the alarm does not generate the alarm signal, and the processor transmits a second notification to one or more mobile devices of the one or more persons indicating that the trigger event has occurred.