Air carrier First Officer reported a hydraulic system failure on final approach to a non-towered airport. The flight landed and stopped on the runway and was towed to the jet bridge.

Narrative

On Aircraft X; we lost HYD SYS 2 on short final. This caused us to land with degraded performance and flight controls putting us in an emergency state. Due to the time the event happened; the Tower being closed and already on CTAF; no formal emergency was declared. After safely stopping the aircraft at the end of the runway; the parking brake was used while checklists; crew Flight Attendant's (FA's); ATC; OPS; DISPATCH; and CTAF were all alerted of the situation and a solution for us being unable to exit the runway was created. After the solution was established; and we could safely shut down the engines; we removed the parking brake to allow the brakes to cool. After a bit of a wait; the ground crew arrived with a tug and towed us to the jet bridge. All passengers exited and the aircraft was shut down with brakes in the green normal indication. Upon arrival in the morning; we were told that two of the tires had gone flat; and the others were coated in hydraulic fluid and all 4 needed to be replaced. Cause: The cause was an unknown mechanical error that happened in a hyper critical phase of flight causing all of our hydraulic fluid in SYS 2 to drain in a matter of minutes after gear was actuated. Suggestions: This type of training should be done in the Simulators; as the jet does not give you a specific failure indication until effected systems were to deploy. After gear is down and you are configured if the system fails without fluid there is not a clear indicator to run an appropriate checklist that would have the crew use the appropriate abnormal landing calculations. The messages that populated were only precautionary for us until we were in the flare/touching down and things like spoilers were to deploy but could not. I have a mechanic training background in aviation; and with the information presented; accurately predicted the failure. I; as a precaution; calculated our landing distance without HYD SYS 2; and asked the Captain if he would like to configure flaps full and follow the new landing speeds as a precaution. I would like to emphasize that we were committed to landing before any caution or warning messages were displayed that would normally trigger the appropriate QRH page and subsequent landing calculation. This combined with adverse weather in the area; and an abnormal fuel indication (FUEL FEED 2 FAIL) encouraged us to make the decision to land the aircraft as the safest option with the landing distance required for a full HYD SYS 2 failure already accounted for and discussed.