As a youth, he shined shoes and raised pigeons, before finding work as a stockboy. He joined the US Military in 1963, and the following year was stationed at Guantanamo Bay, Cuba before being transferred off to spend the following year in the Vietnam War. Some time shortly after 1965, he was sentenced by a Massachusetts state court to five years in prison for armed robbery and assault, serving the last ten months in Massachusetts Correctional Institution - Cedar Junction. He claims it was during these years that he became heavily politicized, through his interactions with other prisoners
After his release in 1971, he married Carol and together they produced three children, Jeremy, Tamara, and Jonathan.
Together with his arrest for the bombings, Manning was also convicted for his role in killing New Jersey police officer Philip Lamonaco during a traffic stop on December 21 1981. The killings launched the largest manhunt in NJ police history, and ended with the arrests of Raymond Levasseur, Patricia Gross, Richard Williams, Jaan Laaman, and Barbara Curzi on November 4th 1984, and Manning and his wife Carol on April 24, 1985. All of them were associated with the United Freedom Front.
He pled self-defense at his trial, while defense counsel showed that Lamonaco had emptied his .357 Magnum revolver at Manning and his associates. He was sentenced on February 19, 1987 to 58 years in federal prison.