A US official says authorities have reviewed a Texas congregation’s video from inside the church showing a man shooting some victims – including children – in the head during morning worship.

Devin Patrick Kelley killed 26 people, including an unborn baby, and wounded 20 more at the Baptist church in the small Texas town of Sutherland Springs on Sunday.

The official’s account of the video on Wednesday is consistent with what witnesses attending the service said about Kelley’s actions during the attack, with the footage said to show the “methodical” nature of the shooting.

The footage was taken as part of the church’s push to record its services and post the videos online.

Law enforcement officials declined to say whether the video would ever be released but one official, speaking to the New York Times on the condition of anonymity, said it showed the shooting lasted seven minutes.

The killer went to the church with magazines capable of holding more than 400 rounds of ammunition, the official told the Times.

The same official confirmed the mobile phone that belonged to the attacker was an iPhone but that the FBI had not yet asked Apple for help obtaining data from the device.

On Tuesday, Christopher Combs, the special agent in charge of the FBI’s San Antonio division, said agents haven’t been able to access the data on Kelley’s mobile phone.

Authorities also released an official list of those killed in the shooting rampage at a Texas church.

Eight male victims and 17 female victims ranging in age from 1 to 77 are on the Texas Department of Public Safety list released on Wednesday.

The list also includes the unborn baby of Crystal Holcombe, identified on the list as Carlin Brite “Billy Bob” Holcombe, age 0 and gender unknown.

Eight of the victims were children and teenagers ranging in age from 1 to 16 years old.

Police reports previously revealed Kelley briefly escaped from a mental health centre in New Mexico in 2012.

The Air Force confirmed on Tuesday that Kelley had been treated in a facility after he was placed under pretrial confinement stemming from a court-martial on charges that he assaulted his then-wife and hit her child.

Also, a police report from El Paso says Kelley was caught trying to bring guns on to Holloman Air Force Base in New Mexico when he was stationed there.