Several other journalists were believed trapped in the embattled city and neither Colvin's remains nor those of French photographer Remi Ochlik, who died in the same explosion, have been recovered.
Her mother called on the U.S. government and the international community to help bring her daughter's body back.
"I won't rest until she is brought home one more time," said Rosemarie Colvin, 79, of East Norwich. "If it doesn't happen today or tomorrow or next week or next month, I am absolutely determined it's going to happen."
Marie Colvin specialized in reporting from war zones. The Oyster Bay High School and Yale graduate wore a signature black patch over the left eye she lost to an exploding hand grenade in Sri Lanka in 2001.
"She devoted her life to bringing out the truth of the horror of wars," said Cathleen Colvin, a younger sister from Oyster Bay. "The thought of leaving her in a war zone is painful to the family."
Schumer said the absence of a United States presence in Syria "has made our effort difficult" as the conflict rages on.
"Marie Colvin is an American hero," said Schumer, adding that he intends "to work every avenue to bring closure to the Colvin family."
Gillibrand spokeswoman Angie Hu said the senator's staff is "doing everything we can to help."
The State Department has reported some progress in negotiations through the Polish embassy in Syria aimed at helping stranded Western journalists, and recovering Colvin's body, but there were conflicting reports Tuesday on the success of those efforts.
The fate of French journalists Edith Bouvier and William Daniels, and Javier Espinosa of Spain, were unknown Tuesday. Bouvier was also believed to be wounded.
Rosemarie Colvin said with a trembling voice that she hopes to get a simple message across to Syrian leaders.
"Do the decent, human thing," she said. "They are our children, they are human beings and we share that humanity with each other."