Miah Cerrillo, 11, told CNN she and a friend called the 911 emergency number from her dead teacher's phone on Tuesday, and waited for what "felt like three hours" for officers to arrive at Robb Elementary School in Uvalde.

The 18-year-old gunman, Salvador Ramos, was inside the school for more than an hour before he was shot dead by US Border Patrol tactical officers.

Law enforcement officials have provided new details of a confusing and sometimes contradictory timeline that has angered and frustrated parents and onlookers who had urged police to charge into the school.

Miah said after Ramos moved from one room into the adjacent one she could hear screams and a lot more gunfire, and the gunman then started blaring music.

The children who survived the attack, which killed 19 students and two teachers, described a festive end-of-the-school-year day that quickly turned to terror.

Samuel Salinas, 10, told ABC's Good Morning America he and other classmates pretended to be dead after Ramos opened fire on the class. Samuel was hit by shrapnel in his thigh.

"He shot the teacher and then he shot the kids," said Samuel, who was in Irma Garcia's class.

Teacher Garcia was killed in the attack and her husband, Joe Garcia, died on Thursday of an apparent heart attack.

Gemma Lopez, 10, was in a classroom down the hall when Ramos entered the building.

She told Good Morning America a bullet came through her classroom wall before any lockdown was called.

Her best friend, Amerie Garza, died in the rampage.

Lifeline 13 11 14

beyondblue 1300 22 4636

Kids Helpline 1800 55 1800 (for people aged 5 to 25)

Australian Associated Press