04/15/2013 at 07:00 PM EDT
In the chaos after the deadly explosions that rocked the Boston Marathon finish line, runners and eye witnesses took to social media to share their experiences.Jeff Chin, 27, of Boston gave his first-person account of watching the terror unfold to PEOPLE's Steve Helling:
I was near the Apple Store, heading to the Dunkin Donuts when I heard it. I was maybe a block away from it, and it was really loud, like a lightning strike had hit really close. And then I heard another one.
People started screaming. I saw a guy with his shirt off, and it was wrapped around his hand and it was soaked red with blood, but I don't think he had lost it. I didn't look too closely.
I saw a woman fall down as she was running away; she was trying to get up and people were stepping all over her, trampling her. She was screaming in pain, but also I think she was terrified.
She was trying to get up, and I saw a guy step right on her hand and she screamed out. I was going over to help her, and then another woman helped her get on her feet.
There was a woman carrying a girl who was maybe 8 years old, way too big to be carried. The girl was screaming, I'll never forget how it sounded. She was screaming, not any words, but just shrieking and kicking and flailing. And I saw that there was blood, but I don't know if it was the mother or the girl. The girl was just terrified.
What you don't see on TV is how loud it was after the fact. Imagine there were hundreds of people just screaming at the top of their lungs, screaming so loud. It was like a sustained scream, collective scream and it went on and on. It was piercing, just the terror that you could hear.
The other thing is that people didn't know which way to go; there's this feeling like, 'Is there going to be another bomb?' That's what everyone was afraid of. I started heading away from the crowd, but the whole time, I thought that maybe I was walking straight into another bomb. I was scared for my life.
It was a nightmare, the worst thing you can imagine.
It was all too vivid and too real [to be a dream]. I knew that it felt like a nightmare, but that I'm awake and that this is really happening. It was like every sense of mine was heightened, I was feeling and seeing and hearing everything. I never want to go through anything like it again, it was terrifying.