One took place in broad daylight in the parking lot at Stoneridge Shopping Center on Sunday, and involved a man, his sister and her husband and their two young children, both younger than 10 years old.
The five had walked to their vehicle in the southeast parking lot around noon after shopping, and the man was about to get into the driver's seat, according to Pleasanton police Sgt. Kurt Schlehuber.
"He was approached by a black male who pointed a gun at him and demanded his cash. The suspect then shoved the gun into his abdomen. The victim gave him the money from his wallet," Schlehuber said, describing the gun as a semiautomatic pistol. "Then the suspect demanded a gold chain, and before the victim could remove it, the suspect grabbed the chain and ripped it off."
The suspect ran and got into the passenger side of a black, 1990s Toyota Corolla; the victim, driving the entire family, gave chase to the two men, Schlehuber said.
"They followed the vehicle westbound on Interstate 580," he said. "While they were on the phone to CHP (California Highway Patrol), the suspect leaned out the passenger-side window and pointed the gun at them.
The family gave up the chase at that point but got the car's license plate, Schlehuber said. He added that the suspect is described as 5 feet 8 inches to 5 feet 9 inches and weighed about 180 pounds; the family could only describe the driver as a black male.
An earlier robbery took place around 11 p.m., Friday, Feb. 17, at the 7-Eleven in the 4300 block of Valley Avenue, according to Schlehuber.
"A lone clerk was in back, stocking the shelves. Three suspects entered, one male and two females -- usually you don't see that," Schlehuber said. He said the male and one of the females were armed with black pistols.
The male, Schlehuber said, "pointed the handgun at the clerk and demanded money, so the clerk gave him money. The two females began to gather cartons and individual packs of cigarettes."
The three were identified as a black male with a slim build, 5 feet 5 to 5 feet 7, with a thin white or Hispanic female, 5 feet 6 to 5 feet 8, and a heavyset black female, 5 feet 3 to 5 feet 5; the black female was armed.
All three were trying to hide their identities, Schlehuber said.
"The male had a black hooded sweatshirt pulled up over his face and a mask so that only his eyes were visible," he said, adding the male was wearing black pants and black gloves.
While neither of the women was masked, Schlehuber said the black female was wearing a gray or white hooded sweatshirt, also pulled up to hide her face, and the other woman was wearing a beige hooded sweatshirt, sunglasses and jeans.
A K-9 unit was brought in to search for the trio and a pack of cigarettes that may have been taken from the 7-Eleven was found at an apartment complex near the store. A witness spotted the three leave, Schlehuber said.
"Both of these cases have excellent leads," he said. "They're obviously top priority and we're working hard to solve them."