SAN FRANCISCO — A 32-year-old woman shot and killed in broad daylight in San Francisco has been identified as Kathryn Steinle, a former Pleasanton resident and Amador Valley High School graduate.

Meanwhile, police said they arrested Francisco Sanchez, 45, of Texas, in connection with the random shooting.

Steinle was walking with her father and a family friend on Pier 14 in the city’s South Beach neighborhood Wednesday evening when she was shot in the back, said her mother, Liz Sullivan.

The gunshot pierced her aorta, Sullivan said, and Jim Steinle, the victim’s father, tried to give her CPR as she lay wounded on the ground.

“She said, ‘Dad, help me, help me,” Sullivan said when reached by phone. “She was so young. This is just like a bad dream.”

Around 6:05 p.m. Wednesday, officers and firefighters responded to reports of the shooting and began giving her first aid at the scene. Steinle was taken to San Francisco General Hospital, where she was pronounced dead, police said.

Officers detained Sanchez at the corner of The Embarcadero and Townsend Street at 7:15 p.m., after several witnesses identified him as the shooter, police Sgt. Michael Andraychak said Thursday at a news conference.

Officers later arrested him on suspicion of killing Steinle, Andraychak said. Sanchez was not carrying a gun when taken into custody, police said.

Sanchez is on probation from a criminal conviction in Texas, but police said they cannot release more details about it until they confirm his fingerprints and date of birth.

Divers from San Francisco police’s marine unit searched the waters near the pier Thursday “to search for evidence that may be related to the crime,” Andraychak said. He declined to say if investigators are looking for the gun that killed Steinle.

There is no known connection between the victim and the suspect, and they exchanged no words before the shooting, police said.

Investigators have not yet found a motive, Andraychak said.

“(Steinle) was here with her family and they were out on the pier enjoying the day,” he said.

Steinle, a San Francisco resident, worked as a sales representative for Medtronic, Inc., a Mountain View-based medical technology company, Sullivan said. She is survived by her parents, who still live in Pleasanton; and her brother, Brad Steinle, also of Pleasanton.

Sullivan described her daughter as a “sweet, beautiful, independent, strong-willed woman” who enjoyed traveling and doing charity work, including hosting a fundraising dinner for patients with multiple sclerosis.

Police said the Steinle family want to thank bystanders who helped give CPR at the scene and stepped forward to describe the suspect to investigators.

Sullivan said that Steinle was very close with her parents and brother, visiting them frequently in Pleasanton and calling nearly every day.

“She’s my baby girl, and she was over here just the other day,”

Sullivan said. “It’s just unbelievable. There are no words.”

Contact Rick Hurd at 925-945-4789 and follow him at Twitter.com/3rderh. Contact Chris De Benedetti at 925-482-7958 and follow him at Twitter.com/cdebenedetti.