Parsons Green Terror Attack - neighbour voxpop

At around midnight, loud shouting was heard outside, but it was ignored, assumed to be someone returning from a pub. The next morning, a police van was seen, initially thought to involve a minor arrest. However, the situation escalated as more police officers and undercover cars arrived, indicating a significant police operation.

What was the narrator's initial assumption about the police presence?

Describe the sequence of events as more police cars arrived.