By Tracy Jarrett, NBC News
As soon as the two deadly bombs exploded at the Boston Marathon, Jeff Bauman said he knew who was responsible -- the man standing next to him.
Bauman remembers making his way through the crowds of Boylston Street on April 15 to support his girlfriend, who was running in the marathon.
“Everyone was clapping and cheering. You know, it's like a fun atmosphere,” Bauman told NBC News’ Brian Williams Wednesday in his first television interview since the bombing.
“You could tell that people were there for the marathon, because everyone was watching, and everyone was talking to everybody. Everyone was interacting with everybody. Everyone was having fun.”
Everyone, he says, except a man standing next to him who stood out.
“He wasn't with anybody, he was standing right next to me.”
That man was later identified as one of the bombing suspects, Tamerlan Tsarnaev. Tamerlan was killed in a shootout with police. His brother, Dzhokhar Tsarnaev, pleaded not guilty Wednesday as 30 survivors and victims' relatives stared him down in the courtroom.
According to Bauman, “[Tamerlan] looked kind of-- wasn't laughing, wasn't having fun.”
In addition to his demeanor, Bauman noticed a bag that seemed out of place.
Seconds after noticing the bag, Bauman said he heard a loud pop. Sitting in a pool of blood, with both legs wounded, he was rushed to an ambulance by a stranger – a moment that has become one of the days iconic images.
But despite his pain, Bauman knew he had to tell police what he’d seen.
“Even in the ambulance ride I was trying to say something, trying to say, like, ‘I knew who did it, I knew what went on.’ And then I think they were kind of thrown back by that. They were like, ‘What? You know what went on? You know what happened?’ And I was like, ‘Yeah, I saw the guy.’ I think that's what I said. I was like, ‘I saw the guy,’” he said.
“I mean, I was going on a hunch. I didn't know it was him, it was just a good hunch.”
That hunch later helped investigators identify Tsarnaev as a suspect.
“I just wanted to get a face out there. And just to help. I just wanted to help,” he said.
Now, nearly three months later, Bauman is recovering from a double leg amputation. He’s receiving physical therapy to help gain strength and learn to use his new prosthetic legs.
While the process is strenuous, Bauman said he tries to stay positive and hopes to have a normal life.
“I just figure you can't be negative about it. Why? Why sit, be negative and be sad and depressed? You got to kind of push everything to the side and just focus on just getting better. That's how my focus shifts to get home. I wanted to get home and be normal again,” he said.
The outpouring of support from strangers has helped Bauman hold on to hope and encouraged him to give back.
Click here to learn how to help
“I really want to do something great. I want to be out there, I want to help people. I want to just help people. That's what I want to do.”