US Park Police were “alone” and “understaffed” while being “assaulted by a mob of thousands” of pro-Hamas rioters in Washington, DC, on Wednesday — some of whom even pelted officers with poop, according to the force’s union chief.

Park Police Fraternal Order of Police chairman Kenneth Spencer told The New York Post in an interview a day after the riot that just 29 of his officers had faced down the terrorist-sympathizing mob outside Union Station — which is just blocks from the Capitol.

“We were primarily alone,” said Spencer, a 15-year veteran who revealed that years of “empty promises” to beef up the agency’s shoestring budget have gone unfulfilled by Congress and the Interior Department, which primarily deals with the nation’s rural national parks rather than civil unrest in big cities.

Rioters tagged monuments with graffiti messages such as “Hamas is coming” and tore down US flags, burning and trying to replace them with Palestinian banners in opposition to Israeli Prime Minister Benjamin Netanyahu’s address to Congress.

Just 10 were arrested by Park Police, an agency spokesperson confirmed, while another nine were taken into custody by DC police.