The Donna, Texas, Independent School District has canceled classes after it received a "credible threat of violence," school officials said in a letter posted on Facebook. Donna is about 4 1/2 hours from Uvalde.

The threat is currently under investigation and classes will resume on Tuesday, the district said.

"In light of the recent events and in an abundance of caution we will be canceling school district-wide and staff will be working from home," the letter said. "The safety and security of our students & staff is our first priority."

-ABC News' Luke Barr

Nine of the deceased victims' bodies were released to funeral homes in Uvalde on Wednesday evening, Uvalde County Justice of Peace Eulalio Diaz told CNN.

More -- possibly all -- of the remaining bodies are expected to be released at some point on Thursday, according to Diaz. It will mark the beginning of the funeral arrangement process for many grieving families in the wake of the second-deadliest school shooting in U.S. history. There are two funeral homes in Uvalde, and both are offering free services to families of the victims.

"My job is to try and get them back home as quickly as possible," Diaz told CNN in an interview early Thursday.

In a county of less than 50,000 people, there is no medical examiner and the justice of the peace in the state of Texas assumes the responsibility of the county coroner, according to Diaz.

Diaz described his job of going in and assessing the bodies of the dead at Robb Elementary School on Tuesday in the immediate aftermath of the mass shooting. He said Irma Garcia, one of the teachers who were killed, was a former high school classmate of his.

-ABC News Ahmad Hemingway

There were four Border Patrol agents, members of elite specialized units, who engaged and stopped the elementary school shooter, along with state and local officers, a Customs and Border Protection official told ABC News.

One agent, who was part of the Border Patrol Tactical Unit, or BORTAC, held a shield as the group pushed toward the gunman's incoming fire, the official said.

Two BORTAC agents discharged their weapons along with one member of the Border Patrol's Search, Trauma and Rescue unit -- all part of the group of four.

At least one BORTAC agent shot the gunman, although it's unclear who among them killed him, the official said.

-ABC News' Jack Date and Quinn Owen

Moments before carrying out the deadly attack at Robb Elementary, the suspected gunman allegedly sent a string of messages to a young girl he met online, detailing that he had shot his grandmother and was heading to the school for his next target, according to messages reviewed by ABC News.

The messages allegedly show the accused gunman, 18-year-old Salvador Ramos, texting with a 15-year-old in Germany who he met on the social media platform Yubo, describing an argument he was having with his grandmother over a phone bill before texting, "I shot my grandmother in the head" and "ima go shoot up a elementary school rn."

"She's on the phone with AT&T," Ramos allegedly wrote at 11:06 a.m., while referring to his grandmother with a derogatory term.

"Ima do something to her rn," he said in another alleged message. Minutes later, the gunman allegedly wrote, "I shot my grandmother in the head" before immediately adding "ima go shoot up a elementary school rn."

The friend did not reply to the accused gunman's messages until news broke regarding the shooting, according to the screenshot reviewed by ABC News.

Speaking to The New York Times, the girl said she only asked a friend in the United States about contacting law enforcement after she saw news of the shooting, telling The Times, “Maybe I could’ve changed the outcome... just could never guess that he’d actually do this.”

Law enforcement sources tell ABC News the messages are part of the ongoing investigation into the shooter.

-ABC News' Will Steakin, Josh Margolin and Aaron Katersky

As President Joe Biden left Mass at a Catholic Church in Uvalde, Texas, on Sunday afternoon, he walked over to a crowed of people outside chanting, "Do something."

Biden looked at the crowd and mouthed the words, "We will."

Biden and first lady Jill Biden attended Mass at Sacred Heart Catholic Church. As they entered the sanctuary, Jill Biden reached out and lightly touched the hands of several people seated along the aisle as she and the president made their way to their seat in the first-row pew.

About 600 people attended the service.

The president and first lady were greeted at the church by Archbishop Gustavo Garcia-Siller, according to the White House.

“In the midst of collapse and devastation, we have come once more to this our house. To pray. And to be together," one of the service leaders said as the Mass got underway.

Garcia-Siller invited children to come to the front of the church and sit.

"They passed away. But you are alive," the archbishop told the children, referring to the 19 students and two teachers killed in the attack at Robb Elementary School on Tuesday.

Garcia-Siller told the children that he believes they will help the community heal. He noted how Jesus died and “rose from the dead," and then went to heaven.

“He prepared a place for the 19 little ones we lost,” the archbishop said.

The archbishop said he has experienced the goodness of people in the wake of the horrific tragedy. He reflected on Jesus’ message of peace, saying, Jesus felt fear and pain, but did not become bitter.

Garcia-Siller spoke of the joy of heaven.

“Our children in Uvalde who left us already join in this joy," he said. “Heaven is open for all."