NEW YORK — A man who admitted plotting to bomb the city's subway system wanted to do so with the help of at least two other bombers during rush hour, when the most people could be killed, police said Tuesday. "This was particularly disturbing," police Commissioner Raymond Kelly said. "It was his intention to be on trains during rush hour period and to kill New Yorkers. No question about it." The man, 25-year-old Najibullah Zazi, pleaded guilty Monday to charges including conspiracy to use weapons of mass destruction and supporting al-Qaida, which he said trained him in Pakistan.