Declaring the investigation at a virtual standstill, Philadelphia Police Commissioner Charles H. Ramsey stood outside a West Philadelphia grocery Sunday where the owner, his wife, and his sister were gunned down Sept. 6 and appealed for the public's help in solving the crime.

Ramsey, describing the killings as the worst in recent memory, said police had neither suspects nor leads in the killing of Porfirio Nunez, his wife, Carmen, and his sister Lina Sanchez.

Ramsey was ringed by relatives and friends of the family, who carried placards reading, "We want justice," and, "We want these cases solved."

"We need to bring some closure and some peace to these families," Ramsey said. "I find it very rare that something happens and nobody knows anything."

Capt. James Clark said the two killers were likely armed and were considered extremely dangerous.

"We know that someone knows who these killers are," he said. "We just need to have someone tell us."

The gunmen rushed into Lorena's Grocery at 50th and Parrish Streets in the city's Mill Creek section just as Nunez, who was celebrating his 50th birthday, was closing for the day. They ordered one of Nunez's daughters onto the floor, and then forced another daughter to open the cash register and give them money. Just then, Nunez, apparently unaware that a robbery was taking place, came from the back of the store and was shot multiple times.

The assailants then went to the back of the store, where they killed Carmen Nunez and Sanchez before escaping. Police said the two gunmen were black, one in his early to mid-20s, the other in his 30s. Both wore dark, hooded sweatshirts.

Mayor Nutter has offered a $25,000 reward for information leading to the killers' capture.

Shortly after the killings, police found a surveillance video from the neighborhood that appears to show the assailants approaching the store, then running north on 50th Street after the robbery.

Moments before the gunmen entered the store, Nunez received a phone call from a person asking whether the store had security cameras. It did not. Nunez quickly hung up, and the gunmen burst in shortly after.

About 50 relatives and friends, who chanted, "We want justice," gathered at the news conference to press authorities to intensify the investigation and urge anyone with information to come forward.

"Do not let these villains run these neighborhoods like they own them; we the people own them," said Danilo Burgos, head of the Philadelphia Dominican Grocers Association.

Nunez relative Javish Sanchez, who lives above the store and who heard the shots and saw the bodies shortly after the killings, said he still was gripped by grief.

"We are doing this because we need your help," he said. "It is very, very hard for me to do this. If you know them, please come forward."