Transcript for Eyewitnesses describe London terror attack

We're joined now by eyewitnesses Bradford and Joanne buck visiting London from Connecticut. Want to welcome you this morning and I know that you are were doing sightseeing and came up from the underground and shocked by what you saw. Tell me what happened. When we came up from the underground right opposite big Ben and parliament, we saw all this commotion going on, looked over, there was a car crashed into the gate. Door open and there was a man down right next to the car all curled up and another person with hands over his head like, you know, couldn't believe what happened and then the next thing I saw was a few police officers with machine guns running around so very, very hectic, this must have just happened when we came up from the underground. Bradford and Joanne, Bradford, you had the idea to quickly take cover. Tell me what you did next. Instinct kicked in, I imagine. Right, it took a few minutes to sink in then when I saw the police with the machine guns this, is not good so I told our friend Kathy and my wife Joanne to get behind some columns that right next to us and get behind that and then we still were in kind of shock and then after another few more minutes I said to our friend Kathy and to my wife, let's get out of here. I know you all are from Connecticut. Unfortunately here in the states we're no stranger to terror attacks in Boston, in New York. But I can't imagine you're on vacation. You're carefree at that moment. Joanne, what were you thinking when you saw what was going on and your husband is telling you to take cover? Just couldn't believe it was happening. Just so surreal. You're seeing what's going on but it's almost not processing at the same time. Just saw the machine guns and knew we had to take cover quickly. After the events unfolded yesterday, tell me about what you all did and what your plans are in terms of staying in London after experiencing the unthinkable there and what is the mood like in London right now? The mood in religion, I mean, the people are great. I mean they're going about their business. There's a lot of police officers with machine guns walking around which we hadn't seen before this happened but the mood of the people, it's great. And, you know, we're going to carry on with our vacation. We're not going to let it stop us. Right. Hope to finish our sightseeing while we are here in London. We certainly wish you the very best. Bradford and Joanne buck, thanks for joining us. So many stand on that bridge to get those iconic photos. We've all been there. Carry on. I love what they said. I did too. Turning to a tragic hate

This transcript has been automatically generated and may not be 100% accurate.