On September 11, 2001, 23 police officers with the New York City Police Department, 343 firefighters with the New York City Fire Department, and 37 police officers of the Port Authority of New York and New Jersey Police Department perished when the Twin Towers collapsed.
Today, the NYPD paid tribute to those first responders with a series of Twitter posts—one for each NYPD officer and several others paying tribute to the FDNY and PAPD, as well as for those who died at the Pentagon and in Shanksville (PA) on Flight 93.