Mackler died Friday after suffering a heart ailment at work in Washington, where he had served as AFP's chief editor for North America since 2006. His sudden death sent shockwaves throughout the agency's bureaus the world over.
"One of the agency's best journalists has died," said AFP chief executive Pierre Louette. "He was for most of us a source of inspiration, a model."
"I know he had a total passion for the agency, a desire for it to be great and remain in the top rank," Louette said. "We will miss him terribly."
Mackler, an American who spoke French fluently, joined AFP in the United States in September 1979 after starting his journalism career at a rival agency, UPI, in New York.
Over his nearly 30-year career at AFP, the indefatigable journalist played a key role in developing the multilingual agency's anglophone service from Paris to the Middle East and Hong Kong.
He was also a passionate and energetic journalist who relished the big stories.
As a reporter or editor, he wrote and oversaw stories that have defined recent history: from the Gulf War in 1991 to the September 11 terrorist attacks in New York and George W. Bush's presidency.
In the past year, he steered the Washington bureau's coverage of the marathon presidential nomination race with his usual vigor and focus in the face of intense competition from rival news agencies.
But between his long hours at the office, Mackler had also dedicated his time and energy to lending his vast experience to journalists working in developing countries.
In 2004, Peter Mackler set up Global Media Forum, an international media training programme, that grew out of work he had done for underprivileged children at Duke Ellington High School in Washington.
For the last year, he had worked with the AFP Foundation, a non-profit, and had been preparing a training project for journalists in Lebanon that had been requested by the United Nations.
"Peter Mackler was a man of many parts but to his colleagues he will be chiefly remembered for three outstanding qualities: his uncompromising commitment to the highest professional standards; his deep loyalty to his friends and colleagues; and his dedication to teaching young journalists," said AFP deputy managing editor Robert Holloway.
Born to a Jewish family in Brooklyn on August 22, 1949, Mackler graduated with a degree in psychology and began working as a psychologist for children in his neighborhood before joining UPI in 1973.
After starting at AFP in the United States in 1979, Mackler moved to the agency's editing desk in Hong Kong in 1982 and went on to become the bureau chief in Sydney and Singapore.
His work in Asia helped turn AFP's English dispatches into an essential source of news for newspapers and broadcast media across the region.
In 1991, he was dubbed "General Mackler" for his sure-handed organizational skills during the Gulf War as he helped AFP correspondents arrive in Kuwait City hours before the US Army.
After working in Brussels, he had his first stint as chief editor in Washington in 1994 before becoming the bureau's deputy regional director.
He was then named senior reporter based at AFP's headquarters in Paris to cover terrorism, a job that took him back to New York to cover the 2001 attacks on the World Trade Center and to Pakistan for the war that followed in Afghanistan.
He returned to Washington in 2004 to cover the State Department before being named chief editor for North America two years later.
He is survived by his wife of 31 years, Catherine, and his two daughters, Camille and Lauren.