Kathryn Steinle was shot dead while sightseeing in a popular San Francisco tourist spot. Source: Supplied

The 32-year-old was taking her dad, Jim, to see the sights of her new home city last Wednesday, stopping at Pier 14 on the bustling Embarcadero to take in the breathtaking view of the Golden Gate Bridge.

About the same time, 6.30pm, a man named Francisco Sanchez was also wandering along the Embarcadero.

Having already been deported from the US to Mexico five times, Sanchez, a 45-year-old undocumented immigrant from Mexico was enjoying a new-found freedom in San Francisco, known as the Fog City — a place where illegal immigrants know they can disappear off the radar.

Jim Steinle wrapped his arm around Kathryn’s shoulder to pose for a photo on the scenic waterfront.

Then, without warning, a bullet hit Kathryn Steinle in the chest.

“There was a pop, and Kate went down,” Jim Steinle later told the San Francisco Chronicle.

“She just kept saying, ‘Dad, help me, help me’.”

Steinle’s parents Liz Sullivan and Jim Steinle address the media after their daughter’s death. Picture: Lea Suzuki/AP Source: AP

Jim said the shooting happened so fast, it was hard to fathom it was actually happening.

He immediately started CPR. Bystanders on the bustling pier dashed to the young woman’s side as others shared with police phone-captured photos of the gunman.

That gunman was Sanchez — reportedly high on sleeping pills. He would later claim that he spotted a gun wrapped in a T-shirt near Pier 14. He picked up the gun and it fired.

Kathryn was rushed to hospital but died two hours later.

As her mother stroked Kathryn’s face for the last time, her alleged killer was already in police custody.

Francisco Sanchez is led into the courtroom in San Francisco to hear his charges in relation to the death of Kathryn Steinle. Picture: Michael Macor/AP Source: AP

In court yesterday, Sanchez pleaded not guilty to first-degree murder, with his lawyer arguing the shooting was an accident.

In a further twist, a law enforcement official has since revealed the weapon belonged to a federal agent.

But far from being just another gun killing, the case of Kathryn Steinle and Francisco Sanchez has become a lightning rod. Why Sanchez was free to roam San Francisco in the first place is now at the centre of a fresh and sometimes ugly debate about immigration in the US.

In one corner stands billionaire real estate mogul-turned US presidential hopeful Donald Trump, who believes in building a wall along the Mexican-US border and used his campaign launch to call Mexicans rapists who brought crime into America. His remarks were considered so offensive, Latino hosts of his Miss Universe contest pulled out and he was dumped by TV network NBC.

Sanchez had been in jail in Texas, charged with sneaking back into the country, but was handed over to authorities in San Francisco in March to face a marijuana charge.

Despite a detainer request by Immigration and Customs Enforcement, in April, Sanchez was released under San Francisco’s status as a “sanctuary city” that does not enforce federal immigration laws.

The city’s decision to release Sanchez has come under fire from both sides of politics.

Shooting victim Kathryn Steinle, pictured here with a friend. Source: Supplied

“The city made a mistake, not to deport someone that the federal government strongly felt should be deported,” Democratic presidential candidate Hillary Clinton told CNN. “I have absolutely no support for a city that ignores the strong evidence that should be acted on.”

Democratic senator Dianne Feinstein, a former mayor of San Francisco, has called on current mayor Ed Lee to start cooperating with federal immigration officials who want felons such as Sanchez to be deported.

Meanwhile anti-immigration crusaders have launched on Steinle’s tragic death in their calls for tougher border control.

Trump quickly weighed in on Ms Steinle’s killing, calling it a “senseless and totally preventable act of violence” was “yet another example of why we must secure our border”.

Kathryn died in hospital. Source: Supplied

“Nobody else has the guts to even talk about it,” the Republican presidential candidate said. “The American people deserve a wall.”

His comments have been echoed by Republican politicians, including House Judiciary Committee chairman Bob Goodlatte, who slammed the Obama administration for “releasing criminals back onto the streets”.

“This administration is not enforcing our immigration laws and, quite frankly, I don’t think they care,” Goodlatte said.

“This tragedy in San Francisco — which is repeated every day around the country but doesn’t get this kind of notoriety — is a product of that lack of caring about the rule of law.”

During his presidential kick-off speech, Trump said Mexican immigrants were “bringing drugs, they’re bringing crime, they’re rapists and some, I assume, are good people”.

Trump defended his comments on CNN this week.

“If you look at the statistics of people coming, you look at the statistics on rape, on crime, on everything coming in illegally into this country, it’s mind-boggling,” he told CNN host Don Lemon, citing an article in Fusion.

“Go to Fusion and pick up the stories on rape. It’s unbelievable when you look at what’s going on. So all I’m doing is telling the truth.”

Venting political frustrations can often be difficult for the average Joe, but a family of Mexicans were pushing the envelope in the border city of Reynosa, Wednesday, after creating a pinata in the image of US presidential candidate and billionaire Donald Trump. The Davalos family began creating papier-mache effigies of the erstwhile 'Apprentice' star after Trump made several comments describing Mexican migrants in the US as 'rapists' and 'killers'. The sweeping statements earned the media-star-cum-politician his own pinata, adorned with the star's signature wispy yellow hair and block-red tie. Many US buyers, eager to get their hands and bats on the Trump effigies, have reportedly crossed the border into Mexico just to pick up the pinatas. The models are also selling well among Reynosa locals, according to the Davalos family. The Republican presidential candidate comments caused outrage throughout Mexico and the US, with broadcasters Univision and NBC Universal both dropping the Miss USA pageant, in which Trump stars, from their channels. Macy's department store is also pulling his brand merchandise from its shops following his statement. Trump has since defended the comments in a CNN interview with presenter Don Lemon, saying he was 'telling the truth' about immigration. Trump has yet to make a comment on being semi-immortalised in pinata form.

Lemon pointed out the story was about women being raped, not criminals crossing the border.

“Well, somebody’s doing the raping, Don! I mean, somebody’s doing it! Who’s doing the raping? Who’s doing the raping?” he asked.

Despite Trump’s claims, a new report released by the American Immigration Council this week revealed that immigrants were in fact less likely to commit crimes and end up in jail than people born in the US.

According to data from the 2010 American Community Survey, 3.3 per cent of men aged 18 to 39 who are born in the US have been jailed, compared to 1.6 per cent of immigrants of the same age.

Trump has lost partnership deals with Univision and Macy’s in the wake of his anti-immigration comments. The PGA of America has also announced plans to move its Grand Slam of Golf away from Trump’s Los Angeles course.

Clinton has also smacked down Trump’s remarks about immigrants, adding she was “very disappointed” in the Republican Party for not condemning him more quickly.

But Trump has found a strong supporter — the grieving mother of an American teenager killed in similar circumstances to Kathryn Steinle.

Anita Shaw, whose 17-year-old son Jamiel Jr was murdered by gang member Pedro Espinoza in Los Angeles in 2008, said she was “angry” at the US immigration policy.

“It makes me sad, it makes me angry, it makes me frustrated,” she told the Daily Mail.

“It’s amazing to me that the same incident is still going on today. It’s like, when will the public wake up and do something. And this guy who is running for president, Donald Trump, he’s trying to do something and they’re trying to shut him down.

“I believe in what he’s saying, he’s trying to fix the borders and do all the things people should have done a long time ago.”

Murder victim Jamiel Shaw Jr’s mother said her son died in similar circumstances to Kathryn Steinle. Picture: AP/Shaw family Source: AP

The day before Jamiel’s death, his killer — who is now serving a life sentence — had been released from jail after serving half of an eight-month sentence for assault.

He had lied about his immigration status, which if checked would have made clear he was wanted for deportation, according to the Daily Mail.

“I still don’t understand why it happened, just like what happened in San Francisco, why wasn’t this guy deported after he was released from prison. ‘Sanctuary city’, that’s crazy,” Ms Shaw continued.

“When I heard about the girl in San Francisco, I said, ‘Oh no, not again’. She was so pretty and so young and to be with her father and her brother when it happened, just enjoying her day, and then all of a sudden no more.”

As the fiery debate rages on, and Sanchez awaits his next court appearance on July 22, the Steinle family is still struggling to come to terms with Kathryn’s sudden death.

Kathryn Steinle’s grief-stricken brother Brad. Source: Supplied

Fighting back tears on ABC7, her brother Brad said she was “the most wonderful, loving, caring person”.

“If anybody could take anything from this: if you love somebody, just tell them that you love them,” he said.

Kathryn loved to make people laugh and smile, Brad said. He added he’d miss everything about her.

“We loved Kate, and I will love her till the day I die,” he said. “I had the best sister.”

Shooting victim Kathryn Steinle during her travels. Source: Supplied