Police on Long Island are studying how to react to a situation where a mass shooting is taking place.

The Nassau County Police Department held its fifth active shooter seminar at Adelphi University yesterday. 

Police explained what measures would be taken if a gunman was on the loose at the school.

Attendees also learned prevention methods and to always prepare for the worst.

The seminar was open to officials from all of Long Island's schools, as well as large corporations and hospitals.