A photographer’s account:

When a festival assignment turned deadly People carry an injured person from the Route 91 Harvest country music festival in Las Vegas after gunfire erupted on Sunday night. (David Becker/Getty Images)

After capturing photographs of the final act of the Route 91 Harvest country music festival, I headed back to the media tent to start filing my photographs.

Editor’s note: The following images contain graphic content.

After five to 10 minutes I heard very loud popping sounds and I went outside to see what was happening. A security guy said it was just “fire crackers,” so I went back to work.

The second time I heard the popping sounds, somebody said to me “it was just speakers or sound equipment” and again, I went back into the media tent and continued to work. Then the noises went again, and that was when the crowd started to flee.

Festival-goers scramble for cover during the shooting attack. (David Becker / Getty Images) People seek cover or run after hearing gunfire at the Route 91 Harvest festival Sunday night. (David Becker / Getty Images)

Once the crowd started to flee, I went outside and saw people panicking and running for the exit that was right by the media tent.

I grabbed my camera and went back outside and found a place where I could see what was happening and also wouldn’t be in the way of people, so I stood on a table and started to shoot — thinking to myself still, that this isn’t really happening, it’s just the speakers popping. It was so dark I couldn’t really see what was happening; there were a lot of people crying, speaking on cellphones and ducking for cover.

As the crowd thinned out, I was able to go a little closer to try and see what was going on and take some more pictures, and I’m still thinking to myself “it’s just the speakers, there is nothing going on.”

It was so dark I couldn’t really see what was happening, there were a lot of people crying, speaking on cellphones and ducking for cover. David Becker

There were groups of people helping each other everywhere and a real sense of people running for cover. People were fleeing, they were panicking. The gunfire was sporadic; it would stop and then more shots, then a lull and then more shots.

I could hear people yelling at them to shut off the lights, to be quiet. People were cowering, they were very fearful for their lives. A woman tripped right in front of me, a man shielded a woman with his body before I saw them both get up and run away, a man in a wheelchair was helped to an exit.

I was trying to capture anything that was moving and that had good lighting. That was critical. It was so dark and there was limited lighting; it was really hard to get a sense of what was happening. At this stage, I still just thought it was a speaker popping, so I was trying to capture people’s emotions and a sense of the panic that was around me.

People, at least one bloodied, lie on the ground at the festival grounds. (David Becker / Getty Images) People tend to the wounded outside the festival grounds after the shooting. Many in the crowd used their shirts to stop bleeding or cover victims. (David Becker / Getty Images) Festival-goers run as gunfire continues from a nearby resort. (David Becker / Getty Images)

I went back into the media tent and called my colleague to see if he could find out what was happening, as I still didn’t know what was going on, and he said that he had found out that the police had called a Code Red and set up a perimeter. It was then I started looking at my photographs and what I was seeing was just unbelievable.

It had been so dark outside I couldn’t see the details, I just saw a lot of people laying on the ground thinking they were playing possum, but now I could see people covered in blood and I thought, this is real.

I started looking at my photographs and what I was seeing was just unbelievable. David Becker

When I saw the image of the woman lying on the ground covered in blood, that was when the impact of what I was experiencing hit; when I realized people were dying.

I kept editing and filing my photographs; the power had been cut so I was working off the light of my laptop, until after five to 10 minutes everyone was evacuated and I was escorted to my car. I worked the rest of the night and into the morning capturing the police officers moving in and the wounded helping each other on the streets.

A man in a wheelchair is taken away from the Route 91 Harvest country music festival. (David Becker / Getty Images) A man takes cover after hearing gunfire. (David Becker / Getty Images) Las Vegas police work on a street outside the Route 91 Harvest festival grounds on Sunday night. (David Becker / Getty Images)

When I stop and think, it’s hard to comprehend what I witnessed. I was on autopilot, just doing my job capturing what was happening, which I think is important. Impactful images like these tell a story, they move people to think twice about doing anything like this, they move governments to change policies to prevent horrific acts like these happening again.

I’ve been doing this work for many years, and it is instinct to photograph first and ask questions later. It probably seems irrational to just walk out and take pictures of people running for cover, but that is second nature for a photojournalist.