Members of the clan suspected in one of the worst massacres in Philippine history are believed to be behind the weekend shooting death of an aide for a key witness to the mass killings, officials said Monday. The attack Sunday appeared to be the latest case of harassment and intimidation of witnesses in the Nov. 23 ambush that killed 57 people, 30 of them journalists and their staff who were accompanying supporters of a gubernatorial candidate. Gunmen strafed the center of a southern township, killing an aide to Vice Mayor Rasul Sangki, who runs the town, and wounding two other people, according to Maguindanao Gov. Esmael Mangudadatu. Sangki has testified against the main suspects, including members of the Ampatuan clan who controlled Maguindanao province at the time of the killings. He told the court in January that Andal Ampatuan Jr., a former vice mayor, led a group of more than 100 local police and militiamen who stopped the campaign convoy, shot dead the victims and buried them in mass graves. Ampatuan, nine police officers and two militiamen have denied the charges against them. They are among 198 people charged with multiple murders in the largest criminal case since the country's World War II prosecutions. Justice Secretary Leila De Lima said Sunday's attack was carried out by gunmen who included members of the Ampatuan family. “A group of armed men, including some Ampatuans - grandsons, nephews or uncles - attacked a place where some witnesses are supposed to be housed,” she said. Army troops backed by armored vehicles moved in to prevent an escalation of violence, said army spokesman Lt. Col. Benjie Hao. They also secured about 25 civilians who were hiding in a warehouse after they were caught in the clashes, he said. The administration of newly elected President Benigno Aquino III has promised justice for the massacre victims. The Ampatuans were allied with former President Gloria Macapagal Arroyo, who stepped down last month, and there were accusations of political interference in the trial and allegations that witnesses have been offered bribes not to testify. One man who came forward to testify was gunned down last month before he could be evaluated by government prosecutors.