SAN FRANCISCO — Kate Steinle’s mother has a phobia of speaking in front of crowds.

But when her family announced Tuesday that they were taking legal action against the local sheriff and two federal agencies for Steinle’s death, Liz Sullivan stepped up on a small stool outside City Hall so she could be seen over the phalanx of TV microphones.

“I don’t know what’s come over me,” Sullivan told dozens of reporters. “I feel as though it’s Kate. She has somehow empowered me. I feel her strength, and I know she’s proud of what we’re doing.”

In an emotional news conference Tuesday, Steinle’s parents said they want to hold accountable not just the illegal immigrant charged with her killing but also the public officials who failed to keep him off the streets. On July 1, just moments after taking a selfie with her father on Pier 14, Steinle — a world traveler and social justice activist who had just moved in with her boyfriend in San Francisco — was shot in the back, allegedly at the hands of an illegal immigrant with a history of seven drug felonies and five deportations.

“It too late to fight for our daughter,” Sullivan said, but she hopes their case will ensure the safety of future families and tourists to San Francisco. “This is for humanity, this is for the future, even though ours is gone.”

The killing ignited a national debate over illegal immigration, with GOP presidential candidate Donald Trump using it as a breakaway issue to tap into American angst. It has also prompted several Bay Area cities to review their “sanctuary city” policies, which limit turning over illegal immigrants for deportation.

Juan Francisco Lopez-Sanchez, 45, charged with murder in Steinle’s death, has said from jail that he found the gun, and it fired accidentally. A ballistics expert testified in a preliminary hearing in the murder case last week that the gun was pointed at the ground when it fired, and the bullet ricocheted before hitting Steinle nearly 100 feet away.

No matter how or why the gun fired, the Steinle’s family believes she would still be alive if San Francisco Sheriff Ross Mirkarimi, U.S. Immigration and Customs Enforcement and the U.S. Bureau of Land Management, whose agent’s gun was stolen and used in the killing, did their jobs properly.

“What happened on Pier 14 was not only foreseeable, it was preventable,” said lawyer Frank Pitre.

The Steinles are blaming the sheriff for failing to notify ICE when Lopez-Sanchez was released from jail even though ICE had sent a detention request. ICE, the family claims, also was at fault for failing to send San Francisco a warrant — instead of a request — to detain Lopez-Sanchez, knowing that the San Francisco sheriff was unlikely to hold him without one. Lopez-Sanchez had finished serving a federal prison term when he was sent to San Francisco to face a 20-year-old marijuana charge that local authorities quickly dismissed. That’s when he was set free.

The family is also blaming the Bureau of Land Management, whose ranger was on business in San Francisco four days before the killing. The claim says the ranger left the gun in a backpack “in plain sight” in a vehicle, where it was stolen.

Pitre says San Francisco’s “sanctuary city” ordinance isn’t necessarily the problem.

“There is nothing in sanctuary cities that prohibits cooperation with federal agencies,” Pitre said, explaining that the intent of sanctuary cities is to support otherwise law-abiding immigrants and their families, not felons.

Since Steinle’s death, however, Mirkarimi has defended his actions, saying ICE should have issued an official warrant to detain Lopez-Sanchez. Officials with ICE, however, have said that Mirkarimi doesn’t understand federal immigration law. Mayor Ed Lee, Mirkarimi’s political rival, also has criticized Mirkarimi for releasing Lopez-Sanchez without informing ICE.

The case ignited a firestorm, propelled by presidential candidate Trump, over illegal immigration. And while the Steinle family hasn’t spoken about whether they agree with Trump’s politics, Sullivan said, at least he is taking on the issue. “He’s not like the rest of the people who give lip service” to immigration, she said.

Steinle’s father, Jim Steinle, said he is haunted by his daughter’s last words to him as she lay dying in his arms.

“Help me, Dad,” he recounted.

Jim Steinle said shortly after Kate’s death, the family received calls of condolences from the mayor, sheriff and other public officials, but the silence from San Francisco’s leaders since then “has been deafening.”

Filing these claims might start to help others, he said.

“No amount of money will ever bring Kate back,” her brother, Brad Steinle, said. “But I hope that by us standing here today, we will start the process of change so that people will be safe when they come to this city.”

Contact Julia Prodis Sulek at 408-278-3409. Follow her at Twitter.com/juliasulek.