He is an SPK member and FBI officer.
McEnroe first appears at the beginning of the Near-Mello story arc when he is sent to the Japanese National Police Agency HQ in order to request that the Death Note that they have is handed over to the United States government, and thus the SPK. Soichiro Yagami, Deputy Director of the NPA, accuses the FBI of being involved in the kidnapping of Kanichi Takimura, the head of the NPA, but McEnroe persuades him that this is not the case and they agree to work together in order to rescue Takimura.
Takimura is later found dead and Mello kidnaps Yagami's daughter Sayu, leaving her father with little choice but to go to America and hand the Death Note over to the Mafia. After the exchange is made, McEnroe picks the Yagamis up by helicopter but then takes them to a building in Los Angeles where Near questions them about the kidnappers.
Death Note: How to Read 13 reveals that McEnroe survived the killing of the SPK agents by the use of the Death Note (see Chapter 66 "Death") but he is not seen again in the manga.
(Source: Death Note Wiki)
