NEW YORK >> Police don’t know who he is, where he is, or why he did it.

As the frustrating search for UnitedHealthcare CEO Brian Thompson’s killer got underway for a fifth day Sunday, investigators reckoned with a tantalizing contradiction: They have troves of evidence, but the shooter remains an enigma.

One conclusion they are confident of, however: It was a targeted attack, not a random one.

The fact that the shooter knew UnitedHealthcare group was holding a conference at the hotel and what route Thompson might take to get there suggested that he could possibly be a disgruntled employee or client, NYPD Chief of Detectives Joseph Kenny said.

Police divers were seen searching a pond in Central Park, where the killer fled after the shooting.

— The Associated Press