A bloody weekend in San Francisco left three men dead, with all the killings happening in or near areas where police are trying to curb violence by adding undercover officers to the streets. An attack at 10:45 a.m. Sunday in the Tenderloin left Ralph Ruiz, 59, dead of stab wounds. Investigators said Ruiz had been arguing with a man outside 245 Hyde St. when the man attacked him. The killer was described as a stocky white man, about 5-foot-2, with a white beard and white hair. He was wearing blue jeans, a white T-shirt and blue jacket, police said. The other two slayings were in the Bayview. The first happened at 6:30 a.m. Saturday on the 1700 block of Newcomb Avenue, when Darius Cooper-Brooks, a 26-year-old San Francisco resident, was shot to death on the street. No arrests have been made, and police said there was no description of the killer. At 10:25 p.m. Saturday, Calvin Fennell III, 59, was shot several times on the 100 block of Kiska Road. Fennell died later at San Francisco General Hospital. Police said the killer wore a ski mask and black clothing.Family members said Fennell had been on his way to visit his 14-year-old daughter in the Hunters Point housing development when he was slain. They said the gunman appeared to have been waiting for him, but said they did not know who would want to kill him."He was a good guy," said his mother, Doris Fennell. "He didn't bother no one." A sister, Francine Fennell, said Calvin Fennell had another daughter and a son. "I'm shocked," she said. "I can't really believe it."The Tenderloin and Bayview areas have been the focus of a 6-month-old police crackdown that Chief Heather Fong said last week was showing results. The department is relying in part on flooding streets in the areas with undercover officers targeting the drug trade. So far this year there have been 81 homicides in San Francisco, compared with 82 at the same point in 2007. Ninety-eight people were officially listed as homicide victims for all of last year, but police are still reviewing two deaths that may push the total to 100. SOURCE:SFGATE.COM