Investigators haven't determined whether Cesar Mercado's death was a homicide or suicide, Police Commissioner Raymond Kelly said.
Mercado's body was found Thursday by a driver who had come to take him to his job at the United Nations, where Mercado was general consul.
Mercado, 34, usually arrived by subway at about 7:30 a.m., but when he didn't show up, the driver went to the apartment and discovered the door unlocked. He opened it to find Mercado's body on the ground. His clothes were drenched in blood and he was wearing socks but no shoes. He had been stabbed and his throat had been slashed.
The bathroom sink of the studio apartment was full of blood and two knives were found, a 19-inch knife and a smaller knife inside the sink, police said.
Mercado was stabbed a dozen times in the abdomen, but it appeared from the initial autopsy that some of the wounds may have been self-inflicted, Kelly said Friday. More investigation was needed to determine a cause of death, he said.
Kelly described the slashes as "hesitation wounds," meaning they were not clean, decisive wounds that are often made when someone aims to kill.
"It's something that causes the medical examiner to pause for thought," Kelly said.
Security cameras were not working in Mercado's Bronx apartment building, but police were canvassing the area for any other useable video. Mercado was last seen by neighbors about 3 p.m. Wednesday afternoon. They also were examining cell phone records.
Nicaraguan officials were working with U.S. officials to help in the investigation and arrest those responsible, Nicaragua's Permanent Mission at the United Nations said in a statement Friday.
Mercado's body was being sent back to his home city of Masatepe, Nicaragua, for burial in the coming days.
"The government of Nicaragua expresses deep condolences to the family, and offers all its support and solidarity and joins them in this moment of suffering for the Mercado family," read the statement, which was in Spanish.
Mercado's friends had said Mercado was ill in recent weeks and was diabetic. They also described him as a kind, happy, caring, friendly person who had no enemies.
It was earlier thought Mercado was attending the General Assembly's annual meeting, but officials now say he just had his office at the U.N.