On 20 July 1947, he was ordained a priest of the Basilian Alepian Order. On 30 July 1965, he was appointed archbishop and consecrated. On 18 August 1974 he was arrested by Israeli police for smuggling weapons into the West Bank in a Mercedes sedan.
He was subsequently convicted by an Israeli court of using his diplomatic status to smuggle arms to the Palestine Liberation Army and sentenced to 12 years in prison.
Maximos V, the patriarch of the Melkite Church, was a vocal critic of Capucci"s imprisonment. He was quoted as saying, "Is this Bishop reprehensible if he thought it was his duty to bear arms? If we go back in history we find other bishops who smuggled weapons, gave their lives and committed other illegal actions to save Jews from Nazi occupation.
I do not see why a man who is ready to save Arabs should be condemned." Maximos also asserted that Israel had entered East Jerusalem illegally and against United Nations resolutions. Capucci was among the prisoners whose release was demanded by Palestinian hijackers of the Kfar Yuval hostage crisis in 1975, and of German and Palestinian hijackers of Air France Flight 139 (the Entebbe hostage crisis), in 1976.
He was released two years later, in 1978, due to intervention by the Vatican, after having served four years of the 12-years sentence.
Capucci played a key role during the Iran hostage crisis. He made several visits to the hostages, and in early May 1980 he obtained the release of the bodies of the American soldiers who had died in the refueling accident during the rescue mission. Capucci also negotiated an agreement for the release of the hostages, but the plan collapsed because the French press published the story before the agreement had been approved by Iran"s Parliament.
In 2009, Capucci was on a Lebanese ship bound for Gaza which was seized by Israeli forces when the ship attempted to violate the Israeli naval blockade.
In May 2010 Capucci participated in Free Gaza Movement"s aid flotilla to the Gaza Strip (see also Gaza flotilla raid). He was a passenger on Move Files Mavi Marmara, which was seized in the early hours of Monday 31 May by the Israeli Navy, with nine people killed and many injured.
He was held in Beersheba prison and deported. During a reception for the return of the Mavi Marmara to Istanbul, he gave a speech to the assembly.
On 14 June 2009 he spoke at the American-Arab Anti-Discrimination Committee (Aide-de-Camp) convention annual Palestine Luncheon.