A separate memorial ceremony is expected soon at the spy agency's headquarters.
"There is a collective sense of loss at the agency when you lose seven," said Ted Gup, a journalism professor at Emerson University and the author of "The Book of Honor: The Secret Lives and Deaths of CIA Operatives." "That really sucks the wind out of the agency. They recognize the vulnerability that they all have. It's a high risk profession.
"Historically, the agency has provided letters of condolence to the grieving families and then withdrew them the moment after they were read and placed them in secured personnel files -- for fear that leaving the letters with the families would provide them evidence linking the casualties with the agency itself," said Gup.
The CIA said that practice is no longer used.
Director Panetta offered condolences and a promise in his letter.
"We do more than mourn those taken from us," he wrote. "We honor them, in part by pushing forward the work they did, work to which they were absolutely devoted."