Chilling NYPD audio recorded during

Tuesday’s downtown Manhattan slaughter

includes shaken cops describing the sight of the “mass casualty situation” before them.

“There’s multiple people on the ground, Central. We need buses all the way up to Houston [Street], Central,” one officer says urgently, according to a tape obtained by the Post.

“I’ve got four or five people on the ground.”

Another cop says, “We got multiple casualties. This is a mass-casualty situation here.”

The recording was taken from two-way police radios, CBS said.