People on the streets, as well as traffic. Its a very heavy populated area, of course, of london. London bridge is an iconic landmark within the city. Its very unusual to see anything like this take place in broad daylight. Im currently looking at the police cordon. Police officers are horseback. I see fire trucks and police vans. What we know in terms of what has unfolded here, we saw video posted to social media. One chilling video shows a scuffle on the ground that happened at the bridge area. A shot was fired, presumably by the police, who had their guns raised. And a man seemingly a passerby, just walking off with what appears to be the suspects knife. Police saying they responded to the incident at 1 58 in the afternoon. Theyve made one arrest. That there was a stabbing reported in the area. A number injured as you can hear there, perhaps the police now on horseback trying to clear the area. Again, its a very populated part of london. Give us a little bit of the logistics here, just so people who havent been there can understand the London Bridgetself. Dont want folks who may not be familiar to confuse it. It is an iconic landmark, the London Bridge there. Some people who have been to the east coast of the United States and know the area around the Brooklyn Bridge and what we call the area underneath the Brooklyn Bridge, its kind of similar to that, in that its an area that was once less populated, but has become very, very popular. I go to the burrough market area pretty much ever time i go to london, and what ive noticed is theres almost not a time where that area is not packed wall to wall with people. Thats exactly what im seeing now. There are a lot of people out on the street. Many of them curious to see exactly whats going on. Again, this is a very unusual incident to take place here in london and i think its clear from the response that im seeing, the large security cordon, the fire trucks, the police van, that authorities at this point are taking no chances. This is what i would call a Gold Standard response from the london police. Ive seen in the past from the terror attacks, other attacks in the past, when there is a hint of a possibility of terror as a motive, police have a play book that they follow to the letter. They tend to like to overreact and assess the facts and establish motive later. And at this point i think motive is very much at the heart of the investigation, what led to this incident on London Bridge, that prompted a Police Officer to feel compelled, according to videos posted on social media, to fire his gun, again at the heart of this investigation, which very clearly to me in the scene that i see before me, is continuing. I want to release you for just a couple of minutes. I know youve had some Police Officers nearby and i want to let you have a few minutes to do some reporting. I want to cling in clint watts, who works at the George Washington university. One of the things that we know about big cities like new york and london, many of them around the world, is that they have become extremely well trained and extremely good at responding to incidents that they see as a threat. Yeah, you can see that in this case of london. They were very quick to get there, it seems, based on the video. There was some sort of an incident, they were already at the bridge. And based on the footage, they had responded with weapons. This is london. Not every Law Enforcement officer is carrying a weapon there. They call in squads to handle those sorts of incidents. And what is they clear, theyre taking this as a Major Incident. Theyve secured two areas. They seem to be checking and going through in a very deliberate way. When you see this going on, we always tend to wonder is this part of a terrorist act. And so if that is the case, im sure thats what were trying to figure out now. Is this a criminal act that occurred, terrorism. Weve seen a lot of inspired Islamic State or supporters over the year have knife attacks. It usually comes down to one of two types. They cant access weapons so they try to do something with a truck or vehicle or a knifestyle attack. So im sure Law Enforcement are trying to parse out is this part of terrorism or crime. And if it is part of terrorism, then they always want to start reacting strongly, because could there be copycats or accomplices, could there be other people in the area they want to detain or question or try to move on to prevent any future sprviolence. Im sure theyre trying to make sure the area is secure and move aggressively on any potential leads. You may be more familiar with the terminology than i am. Were just being told that London Ambulance officials are calling this a Major Incident. I dont know what that means, if there was a major response in terms of the number of people or if its a Major Incident in terms of the number of people who may have been hurt. Whats not clear from the siddio is you see one sufficiently with a single individual on the bridge but you dont know if there were other incidents of violence leading up to that. If there was a stabbing spree, which weve seen in other attacks, not just in london and europe, but even around the world in terms of extremists. So that makes you wonder is this more of a terrorism angle that theyre looking at. If its a Major Incident it could mean more than one casualty or more than one person has been wounded and theyre trying to deal with that situation. And that seems like that could be the case here. That moment that you mentioned, the scuffle, we have that on tape. I just want to tell people that this will stop before hes shot. Lets just take a look for a moment. And if you want to sort of follow along with us here, clint. Yeah, whats really strange with this incident is that you see Law Enforcement eventually trying to remove someone from that scuffle, and then what appears to be the shooting. Its a little bit difficult to understand, seemed to occur after they removed the individual. So its almost as if the assailant was attacking someone and the person being attacked was removed from the situation and then there was some sort of a shooting there. Its a little confusing to understand. But it seems like the person that was doing the attacking was very aggressive and Law Enforcement in europe, they are very rarely carrying weapons, so they call out the squads to actually respond. And they took action very quickly, which means that they probably had some sort of inclination what that individual was about to respond in that way. And its a rather bizarre episode because there were so many people on the bridge filming this incident. You probably could see three or four different videos. This one here you see the entire group is surrounded and the shooting incident happens at the end, which is very strange. Thats not what you might normally see in a Law Enforcement situation. Jim cavanaugh, as you watch this footage, what did you think . It looks like some passersby maybe were in a fight with an attacker or you could have two groups fighting or you could have citizens intervening in an assault. Like clint says, motive unknown. Ive been to london and worked with the metropolitan police. Ive spent a lot of time with them there and studied their Violent Attacks and firearms related attacks with atf. And just the way assaults occur and terrorist bombings and all of the things theyve dealt with in firearms related matters, they have a lot of knife attacks and sharpedged instruments attacks in england as a whole. Much more than were used to in the United States. We have more prevalence of firearms, they do not. Their firearms laws are very strict. So theres a lot of knife attacks. Police officers are often attacked with knives, machetes, axes. And its a weapon of choice. And also as clint said, terrorists have used that weapon as well as firearms, vehicles, bombs. So we dont quite know, chris, how it started. And we do know that all of the bridges in london, as you point out, clearly this is not tower bridge or westminster bridge, this is London Bridge. And the thames has a series of bridges in Downtown London all around. Its an urban area with a river, you know, deeply in the middle from olden times. So theres plenty of bridges there. This is one London Bridge. And as you pointed out, the market, which is a popular area for terrorists and locals for all kinds of shopping, is there as well. So it looks like the police theres a lot of armed police in the metropolitan police near the tourist sites. Obviously theyve already secured the scene, because as you say, theres a presence there anyway. Its a heavily traversed area. But in terms of finding out what this is, and always in the early minutes when Something Like this happens, you know, people dont know if its anything on one hand from a domestic or somebody who has Mental Health issues, all the way up to terrorism. What are they doing right now, jim, to figure that out . Yeah, theyre going heres the simple thing. Were in a hightech world, but its all police work. Its shoe leather on the pavement. We go right to the assailant and take out his wallet and see who he is and start working it back as quick as you can back to his residence, his family, neighbors, associates, his police record. And thats all spun up right now. Met troe theyre looking ought aat all of the units, who is this guy. And then also the witnesses. The witnesses are key. What was happening . Was it a fight between two men . Was it something over some local dispute . Was it yelling things, what some terrorist might yell . Hate affiliated speech or claiming some other affiliation. We could hear all that from witnesses. So thats what theyre doing right now. Detectives are heavy and of course theyve got to secure the area, because could he have an associate or could there be somebody else involved. Those are all questions that the police dont know at the moment. Joel reuben is with us as well. Hes former district secretary of state. A lot of americans live there and visit there. What would be happening on the u. S. Side when Something Like this happens . Chris, right now what the state department would do is issue a public statement, an advisory about whether or not theres a danger in a certain area, and to warn american citizens there. And frankly, this also speaks to a bigger issue about the fact if its confirmed its a terrorist act that the fight against terrorism is not over. So for the state department this is where people get called into action in headquarters in particular, across different bureaus to make sure that any engagements that could be identified potentially, be it syria, in iraq, as were watching right now, afghanistan, are there any connections that they need to make . Are the embassies speaking to their counterparts . Is there a global angle to this as well . That needs to feed into the system for the decisionmakers. We should point out that President Trump is just back from his unannounced visit to afghanistan, but presumably, if he hasnt been already, he will be updated wherever there is an incident like this. Particularly, again, in a place like london where this can be a heavy concentration of americans living and visiting there. He would vet updated on the very latest information on what they think is exactly happening. Clint watts, were watching this is the other thing that happens in situations like this. Its become a way for people to record things for social media, which obviously complicates things for officials who have to cordon off the scene, who want to keep people back. I dont think weve gotten it all clear here, even though we saw the one man being subdued. Tell us a little bit about the logistics of Something Like this kind of combining those two things, about securing the area, making sure that everybody who, instead of staying away from the scene as the state Department Might say, want to go to the scene along with the investigation. Yeah, whats interesting about london is theres probably no city in the world well, with the exception of maybe a few now that we know about in china and other places in asia that has more cc tv cameras that are placed in and around these areas. So while we do see social media shots, many of them taken immediately after the fact or when they see someone responding, london has a remarkable ability in terms of their Law Enforcement to look at almost any spot in london and see whats going on at any given time. Theyve done that already then . They probably already have a good understanding of the situation as it played out and are probably just trying to follow up on leads and evidence right at the immediate time. I want to go back to london. Erin mclaughlin has gotten in front of the camera for us. Give us the latest on what youre seeing and hearing there. Reporter Central London, and just over that way you can see armed officers and police dogs. And what theyve been doing is going up and down this street, clearing the area. You can see there over that way, Police Officers on horseback. And theyve been clearing out this entire area of traffic and pedestrians. Just over that way is London Bridge where the incident in question took place. And just that way you can see is an overground train station. You can see the Christmas Trees in the window. People here lining the street and looking at the scene unfold. An Incredible Police presence and dogs sweeping this area. Why . We do not know. What this is is a sort of textbook response on the part of metropolitan police when they suspect an attack. We do not know the motive. We do not know the circumstances behind what unfolded just a few blocks that way on London Bridge. But authorities very clearly are taking no chances in all of this. When they suspect the possibility of even terror, this is their response. Its called a Gold Standard response. They spare absolutely no expense. And thats what were seeing right now as they try to clear and secure this area, a very busy part of Central London. Erin mclaughlin, thank you very much. Im just also seeing that sky news, which is a major provider there, is saying at least one person was killed in this incident. Nbc news has not been able to confirm that. We are also flooding the scene and getting our crews and reporters there. Were going to take a quick break and keep your panel here. We have some of the best people to understand all this stuff with us and well be back after a short break with the very latest from london. Stay with us on msnbc. Doug with this key to the city. [ applause ] its an honor to tell you that Liberty Mutual customizes your Car Insurance so you only pay for what you need. And now we need to get back to work. [ applause and band playing ] only pay for what you need. Liberty. Liberty. Liberty. Liberty. cause no matter how far away for you roam. Ys. When you pine for the sunshine of a friendly gaze. For the holidays you cant beat home sweet home. The United StatesPostal Service goes the extra mile to bring your holidays home. 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You came back there is a major response number london right now to an incident that involved at least one man with a knife, and what youre looking at is the area around London Bridge, one of the most iconic areas over the thames in london and a big area beneath it, a market filled with food shops and restaurants and is a very heavy pedestrian area in london. Sky news in london, we have not confirmed this, but sky news is reporting at least one person was killed in the incident. What we do already have is some video from the scene and well show it to you, of a man being taken down on London Bridge. But we dont know how this started, what might have precipitated it, or what exactly is going on right now, except that there is a Major Investigation that is going on. We continue to have Jim Cavanaugh with us, joel rubin, clint watts. Clint, im going to assume that when you have Something Like this and until we know what the motivating factor is, does the possibility still exist that this might be a terrorist attack, that in addition to this what we call the