Committee member Mijbil Issa and adviser Dhamin Hussein al-Obeidi, as well as one of their bodyguards, died in a hail of gunfire outside a Baghdad restaurant on Tuesday.
Two other Sunnis have already quit the commission, citing threats from Iraqi insurgents and a general lack of safety.
Kamal Hamdoun, one of the remaining Sunni members, said the 12 other representatives would meet Thursday with Sunni leaders to decide what to do.
"Our membership has been suspended temporarily until tomorrow when we meet the committee that chose us," the Associated Press quoted Hamdoun as saying. "We don't have security."
But at least one Sunni member of the committee, who requested anonymity because of fears for his safety, told the New York Times he would continue to work on the constitution.
"We need to discuss our reaction to what happened, but I can tell you that we will continue working in the constitution committee," he said.
The government of Prime Minister Ibrahim al-Jaafari issued a statement saying, "The government promises everyone that it will punish those killers and will continue supporting and encouraging a wide and comprehensive participation of all parties in drafting the constitution."
Despite these political setbacks, the leaders of the constitutional committee said they felt their work would continue and they still hoped to meet next month's deadline.
"A draft will be presented to the national assembly in the first week of August," Sheikh Humam al-Hammoudi told a news conference in Baghdad.
He said work was proceeding and that key subcommittees would likely complete their sections of the document in the next two days.
"After it is discussed by the national assembly and final changes are made, five million copies will be distributed to households ... on August 15," al-Hammoudi said, according to Reuters.
The New York Times also reported that at least one chapter of the draft constitution could curb women's right, saying that woman would have equal rights as long as those rights did not violate Shariah law -- a more stringent and conservative Islamic law.
The constitutional maneuvering came as violence continued to flared throughout the country.
In the deadliest attacks, six people were killed and at least 25 injured when a suicide bomber attacked an army recruiting center in western Baghdad. In the southern city of Basra, Reuters reported Hussein Hameed al-Darraji, vice president of Basra municipality, was shot dead by gunmen early this morning while leaving his home.