Uvalde police officers responded to the shooting "within minutes," Uvalde police said in a statement Thursday.

"Our personnel have displayed the upmost commitment to our community during this difficult time as we all are suffering as members of the community, that is the family of Uvalde. It is important for our community to know that our Officers responded within minutes alongside Uvalde CISD Officers," Daniel Rodriguez, Uvalde chief of police, said in a statement.

"I understand questions are surfacing regarding the details of what occurred. I know answers will not come fast enough during this trying time, but rest assured that with the completion of the full investigation, I will be able to answer all the questions that we can."

Rodriguez added, "I know words will never ease the pain that we are all suffering, but I hope you will join me in taking some solace in knowing that the pain comes from the fact that we all have such deep love for all the victims who have been taken from us, those who are recovering, and those who only time and love will continue to heal."

Joe Garcia, the husband of teacher Irma Garcia who was killed in the shooting, died of a heart attack on Thursday, according their nephew and a close family friend.

The two were set to celebrate their 25th anniversary this year. The couple had four children.

-ABC News' Alondra Valle

Evadulia Orta, the mother of 10-year-old Rojelio Torres, a fourth grader who died in the Tuesday shooting at Robb Elementary, told ABC News that she is trying to stay strong for the rest of her children, but "I lost a piece of my heart," she said.

The mother of four told ABC News she went to pick up two of her children at the school, but only came home with one.

This has not only devastated her entire family, but the community, she said, speaking with her twin sister.

"We are praying for everyone, all the children and all the families," she said.

-ABC News' Maria Elena Salinas

Bob Estrada, who lives across the street from Robb Elementary School, recounted to ABC News the moments he went out on his porch after hearing gunshots, saying he witnessed the police response to the shooting unfold.

Estrada, whose grandson is a second grader at the school who survived the shooting, said he saw "quite a few" officers outside the school immediately, and then police cars started driving up -- but "some of them just stood there."

"Why aren't they going in?" Estrada told ABC News he wondered at the time.

Estrada said it was not long before parents began to arrive. "They were hysterical," he said.

"There were parents out there, and they were kinda motioning like they wanted to come in," Estrada said. "They were motioning like, 'What are you doing? Go in!'"

Estrada said he did see some officers go in immediately.

Asked if he saw reinforcements heading into the school, Estrada said no. But, he did not know what sort of presence may have already been inside.

-ABC News' Matt Gutman, Olivia Rubin, Jeffrey Cook and Laura Romero

When federal agents from Customs and Border Protection and Homeland Security Investigations arrived at Robb Elementary School Tuesday, they immediately encountered a scene of confusion and chaos, according to multiple law enforcement officials briefed on the attack.

Some arrived with heavy equipment, others with whatever they could carry as they ran to the scene on foot.

Initially, these agents, multiple law enforcement sources told ABC News, tried to discern who was doing what, where was shooter who was engaging law enforcement and how were children were being evacuated.

Once the tactical team assembled with enough gear, they became aware of an order not to enter the classroom because they were told the suspect had barricaded himself, the sources told ABC News.

The Texas Department of Public Safety has said the incident commander wrongly believed the shooting had stopped.

Eventually, the special agent-in-charge of Homeland Security Investigations gave the instruction to all federal agents under the umbrella of the Department of Homeland Security that they were free to use their best judgment and to do what they felt was best, the sources said.

The federal agents were unsure whether any children could be saved at that point, but they were interested in evacuating the wounded. Some agents brought children in other classrooms out through windows.

The tactical team went in at 12:50 p.m. CDT and fatally shot the suspect, 77 minutes after the shooting started, officials said.

The suspect was dead at the scene, the sources said. He was found with more than a dozen bullet wounds.