Hundreds of mourners have turned out for the funeral of Amerie Jo Garza, a smiling 10-year-old killed a week ago when a gunman stormed into her primary school and opened fire.

Her service was the first since the massacre in Uvalde, Texas, with Maite Rodriquez's to follow - plus 19 more over the next two and a half weeks.

Erika Santiago, her husband and their two children wore purple shirts adorned with images of the victims for Amerie's funeral.

She described the youngster as a "nice little girl who smiled a lot" and was "so humble and charismatic but full of life".

Ms Santiago said her son Adriel, 10, watched in horror when news reports first showed images of people killed by 18-year-old Salvador Ramos and he recognised his friends Amerie and Maite.

"He told me he did not want to go to school fearing that could happen," she said.

"He told me, 'Mom, I just don't feel safe.'"

Visitation for one of the teachers, 48-year-old Irma Garcia, was also held on Tuesday, along with visitations for children Nevaeh Bravo and Jose Flores Jnr.

Vincent Salazar's 11-year-old daughter Layla has the last of the scheduled services - her visitation is June 15 with a funeral the following day.

Mr Salazar said the family likely will not see Layla's body until soon before the visitation.

"I understand there were other children as well, but we're just waiting to get her back," Mr Salazar said.

"That's all we're focused on."

Uvalde County justice of the peace Eulalio "Lalo" Diaz Jnr said the bodies of all 21 victims were first sent to the medical examiner's office in San Antonio for post-mortem examinations, which he said is standard for a major crime.

Then, because there is not enough space at Uvalde's two funeral homes, many bodies were sent to out-of-town funeral homes until services near.

The Uvalde funeral homes are working with the families on when they can see their loved ones, he said.

"It's mainly because of the number of victims," Mr Diaz said, asking: "Where do you store that many people?"

Mr Diaz said the post-mortems are complete.

He declined to discuss preliminary results and said final reports will take three to four months.

Mr Salazar said he and his family are going to as many visitations as they can to pay respects to the other victims and their families.

"Not necessarily going to the funerals because we're still taking care of things hour by hour, day by day, here," he said.

"We've got so much stuff going on with our own. You have to set everything up - obituaries, death certificates, funeral arrangements.

"That's all we're focused on right now - her, getting her back and being able to put her to rest," Mr Salazar said of Layla.

"That's it."

Investigators continue to seek answers about how police responded to the shooting, and the US department of justice is reviewing law enforcement actions.

The blame for a delay in killing gunman Ramos - even as parents outside begged police to rush in and panicked children called 911 from inside - was placed on the school district's homegrown police chief, Pete Arredondo, after the director of state police said Mr Arredondo made the "wrong decision" not to breach the classroom, believing Ramos was barricaded inside and children were not at risk.

Steven McCraw, head of the Texas department of public safety, said on Friday that after following Ramos into Robb Elementary School, officers waited over an hour to breach the classroom.

The revelation raised new questions about whether lives were lost because officers did not act faster to stop the gunman, who was ultimately killed by Border Patrol tactical officers.

State police said on Tuesday that the teacher who at one point propped open an exterior door to the school had closed it before the gunman used it to get inside.

However, the door did not lock, police said.

Authorities originally said Ramos came in through the door she had propped open.

Instead, investigators said the teacher, who has not been identified, closed the propped-open door when she realised there was a gunman on campus and ran to get her phone and call 911, said Travis Considine, chief communications officer for the Texas department of public safety.

Investigators are looking into why the door did not lock.

Jacob Albarado, an off-duty Border Patrol agent who rushed to the school with a shotgun borrowed from his barber, said on Tuesday it was chaotic when he arrived in search of his daughter and wife.

Both were physically unharmed in the attack, he said.

"To me, I believe everyone there was doing the best that they could given the circumstances," he told NBC's Today Show.

"I believe everyone there was doing everything in their power."

Authorities said Ramos legally bought two guns not long before the school attack: an AR-style rifle on May 17 and a second rifle on May 20.

He had just turned 18, permitting him to buy the weapons under federal law.

US President Joe Biden's long-planned meeting on Tuesday with New Zealand Prime Minister Jacinda Ardern shifted to gun control after what happened in Uvalde and a week earlier in Buffalo, New York, where 10 black people were killed by a shooter espousing racist "replacement theory".

Ms Ardern won passage of gun control measures after a white supremacist killed 51 Muslim worshippers at two Christchurch mosques in 2019.

Less than a month later, the country's politicians voted in favour of banning military-style semiautomatic weapons.

Mr Biden told reporters he "will meet with the Congress on guns, I promise you", but the White House has acknowledged that winning new gun legislation will be an uphill climb in an evenly divided Congress.