I was there only 5-10 minutes after the accident, an ambulance was there but the first cops (who were probably patrolling Brixton High St) were just arriving. There were already a lot of people looking on. I didn't see /anyone/ take a picture on their camera phone. Lots of people were watching from the raised grassy area in front of the Ritzy and on the pavement in front of that. More people were standing in the street on all sides of the van. It seemed like some of Naomi's friends / people who were already hanging out in front of Ritzy were a lot of the ones standing in the street. Just when I arrived several people were lying on the floor trying to see under the van. None of these were taking pictures, I am sure they were all trying to find out how Naomi was.
At this point, (a couple of cops had arrived), the passenger window of the van had been broken. I saw maybe 3 or 4 people throw things at the van the whole time I was standing there, over about 20 minutes including someone who threw their drink (but not the container). A few people shouted things at the driver, but there was no 'chanting' let alone a 'chanting mob'. A lady bent back the drivers windscreen wipers. Although the driver looked very worried, I didn't see anyone try to get him out of the van, enter the van or specifically try to attack him physically. On several occasions as the police tried to push people back away from the van there were small scuffles. But there wasn't any 'riot', and although the situation was very tense, the amount of pushing there was never really looked as if it was going to become a confrontation between the people and the police.
I think that given the time of day there were a lot of people coming from the station or waiting for buses, and so there was quickly a huge amount of bystanders, but not a big gathering of furious people or ones who wanted to take on the police. As the police gradually pushed people back, first from the road, then the pavement and the grass, some of them objected to being pushed away, but there wasn't any violence. The police claimed that a medevac helicopter which was in the air was going to land next to the van (although I don't think it did), so people wanted to make space for it.
I am posting this since I have seen coverage, some of it linked to from here, mentioning things like mob violence, chanting, riots etc. Of course some people, including Naomi's friends, were very angry, but given the circumstances of the incident, not hugely more than people often get at traffic accidents. The police may have (and probably did) push people out of the way, but not unlike what you would expect in some crowd control situations. There was a very big number of officers there very soon after the first ones arrived, perhaps they thought some kind of riot was likely and so acted very fast.
Partly in response to some debate on the other thread, but I thought this was a better place for it.