Four people were killed, including a police officer, and one was seriously injured when a gunman opened fire inside an office building before killing himself.

Former FBI Special Agent Vito Roselli said one of the biggest challenges with safeguarding city buildings is that many lobbies are open to the public.

Rep. Nicole Malliotakis spoke with Fox News Digital after the deadly shooting that left multiple people including a police officer dead.

The Park Avenue office building where Monday's shooting occurred remains closed, as Midtown workers expressed anxieties about recent violence.

Gun rights, which are protected by the Second Amendment of the U.S. Constitution, are a virtually untouchable issue for Republicans, who control the White House and both chambers of Congress and strongly oppose any encroachment on them.