Authorities have arrested a man they claim was plotting to detonate pipe bombs, New York Mayor Michael Bloomberg said Sunday night.

The Manhattan man’s intended targets were U.S. military personnel who had served in Iraq and Afghanistan, as well as U.S. postal facilities and police stations, a source close to the investigation said before the mayor’s announcement.

The suspect allegedly learned how to make a pipe bomb after reading Inspire, the al Qaeda terrorist network’s English-language online propaganda, recruiting and training magazine, according to the source. He is believed to have been acting alone.

He’d acquired all the material need for the explosive device, going as far as drilling holes into the would-be pipe bomb in an informant’s apartment, the source said. But while he’d allegedly made plans for his attacks, the explosive device was not yet operational.

The alleged would-be attacker, who is believed to be of Hispanic descent, had been monitored by the New York Police Department for about two years, according to the source. The same source added that the suspect had converted to Islam and recently had begun talking about waging a “jihad” consistent with his devotion to the religion.

The FBI was never brought in to assist New York authorities on the case, according to the source.

Bloomberg was joined at a news conference to announce the arrest by New York Police Commissioner Ray Kelly.