"I don't know how the kid knew about the shooter but he was running around trying to tell people and they were paying no attention," Specialist Oakley said.
Cielo Vista Mall.
"Hands up! Hands up! Hands up Let's go! Security officers can be heard screaming at customers as they are herded to safety.
"Run, run, run! Go! Go! Go!"
Many shoppers in the footage appear elderly or very young and children can be heard crying in the background.
Specialist Oakley said the gunfire sent people running in every direction, resulting in youngsters being separated from their parents.
"I walked into Foot Locker and I just heard two gunshots and a whole bunch of people just started running around screaming and they set down their (security) cage," he said.
"I'm from the military so when you hear gunshots we're trained to think fast and grab your weapon.
"A couple of (security) guys ran out of Foot Locker and I'm thinking I'm probably the only one who's legally licensed to carry a gun so I follow them thinking I can guard them.
"And there's a whole bunch of kids running around with out their parents so all I could think of to do was to pick up as many kids as possible. There was another guy doing the same thing.
"There was a total of about 13 kids running around and I could only get three and I think the other guy got about three too. I was just focused on the kids I wasn't really thinking about myself. I just put my head down and ran as fast as I could.
"There were just so many kids running around I kept just thinking if I had a child I would want someone else to pick them up."
Authorities say the Walmart near the Cielo Vista Mall where 21-year-old accused gunman Patrick Crusius allegedly opened fire was filled with back-to-school shoppers.
El Paso Police Sergeant Robert Gomez said the mall was "at full capacity" with between 1000 and 3000 people inside the complex when the rampage began.
He said most of the victims were shot at the Walmart but the initial police response was hampered by a flurry of false reports of shootings at other shopping centres.
"During the active shooting at Walmart we had had multiple reports of other shootings but we now know they are false," Sgt Gomez said.
Walmart spokesman Randy Hargrove says the company is "in shock" over the news of the attack.
The mass shooting in El Paso came less than a week after a gunman opened fire on a California food festival.
Santino William Legan, 19, killed three people and injured 13 others last Sunday at the popular Gilroy Garlic Festival, and died of a self-inflicted gunshot wound.
Ryan Mielke, a spokesman for University Medical Center of El Paso, said 12 people were brought to the hospital with injuries, including one that died.
Two of the injured were children who were being transferred to El Paso Children's Hospital, he said. He declined to provide additional details on the victims.
Eleven other victims were being treated at Del Sol Medical Center, according to hospital spokesman Victor Guerrero. He said those victims ages ranged from 35 to 82.
Texas Governor Greg Abbott called the shooting "a heinous and senseless act of violence" and said the state had deployed a number of law enforcement officers to the city.
A family of three was among a dozen people waiting outside a bus station.
They were trying to return to their car that was in a blocked-off Walmart parking lot.
"I heard the shots but I thought they were hits, like roof construction," Adriana Quezada, 39, who was in the women's clothing section of Walmart with her two children, said.
Ms Quezada said she saw four men, dressed in black, moving together firing guns indiscriminately. Police confirmed only one gunman.
She said her 19-year-old daughter and 16-year-old son threw themselves to the ground, then ran out of the Walmart through an emergency exit. They were not hurt.
Police said by mid-afternoon that a suspect was in custody and the public was no longer in danger.
Sgt Gomez said the suspect, who used a rifle, was arrested without incident. Police believe he was the "sole shooter" but are continuing to investigate reports that others were involved.
White House staff said President Donald Trump was briefed on the shooting and
spoke about it with Attorney-General William Barr and Governor Abbott.
"Reports are very bad, many killed," the president tweeted.
