Run, hide and fight is what retired NYPD Detective Phil Grimaldi says people should do if they find themselves in an active shooter situation.

Grimaldi says the officer who was fatally shot Monday in Manhattan did not have much of a fighting chance against the shooter.

Police officials say 27-year-old Shane Tamura walked into 345 Park Ave. Monday and killed four people, including an NYPD officer and a security guard.

Police officials say he then went up the elevator and shot another person - who is in the hospital - before killing himself.

Detective Grimaldi says the gunman appeared focused and determined on eliminating anyone who would get in front of his goal. Police say that goal was to get to the 33rd floor of the building to the NFL headquarters.

"I think because of the element of surprise so quickly. He entered and he did just open fire, and he was able to take out probably the two strongest security and safety protocols," said Grimaldi.