The state agency investigating the mass shooting at an elementary school in Uvalde has determined that the commander facing criticism for the slow police response was not carrying a radio as the massacre unfolded, a Texas state senator said Friday.

Sen. Roland Gutierrez told The Associated Press in a brief telephone interview that a Texas Department of Public Safety official told him school district police Chief Pete Arredondo was without a radio during the May 24 attack by a lone gunman that left 19 students and two teachers dead. Seventeen more people were injured.

Authorities have not said how other law enforcement officials were communicating with Arredondo on the scene. Arredondo heads the district's small department and was in charge of the multi-agency response to the shooting.

Arredondo has not responded to multiple interview requests from AP since the attack, including a telephone message left with the school district police Friday.

Focus has turned to the chief in recent days after Steven McCraw, the head of the Texas Department of Public Safety, said Arredondo believed the active shooting had turned into a hostage situation, and that he made the "wrong decision" to not order officers to breach the classroom more quickly to confront the gunman.

Gutierrez, who represents Uvalde, complained Thursday that Arredondo was not informed of panicked 911 calls coming from students trapped inside a classroom where the gunman had holed up. The Democrat called it a "system failure."

Police radios are a crucial source of real-time communication during an emergency and, according to experts, often how information from 911 calls is relayed to officers on the ground. It's unclear who at the scene was aware of the calls. Uvalde police did not respond to questions about the calls Thursday.

The Department of Public Safety on Friday referred all questions about the shooting investigation to Uvalde-area District Attorney Christina Mitchell Busbee, who did not immediately return telephone and text messages seeking comment.

The gunman in Uvalde, 18-year-old Salvador Ramos, spent roughly 80 minutes inside the school, and more than an hour passed from when the first officers followed him into the building and when he was killed by law enforcement, according to an official timeline.