LONDON — British authorities made 12 arrests on Sunday after seven people were killed and 48 more were injured an attack that took place in the heart of London on Saturday night.

Three suspects were shot and killed by police within eight minutes of the first emergency call being received. The suspects were wearing fake suicide vests at the time of the attack. The BBC reported that eight police officers fired 50 bullets at the suspects. A member of the public was also shot and injured.

“Indeed I am not surprised that faced with what they must have feared were three suicide bombers — the firearms officers fired an unprecedented number of rounds to be completely confident they had neutralised those threats,” Assistant Commissioner Mark Rowley said in a statement. Rowley confirmed the police force will use “increased physical measures” to protect the public.

Five men and seven women were arrested on Sunday morning in Barking, east of London, where the suspects allegedly lived in. A 55-year-old man has been released without charge.

People who claimed to be neighbors of one of the suspects told the Guardian that he had lived in the ground floor flat with his wife and two young children.

Another man identified as 26-year-old market analyst Ken Chigbo told the Guardian that he had met the suspect who appeared to be dressed in an Arsenal football shirt in the pictures on the afternoon before the attack. Chigbo said he had played football or table tennis with the man and he was “very sociable” and “friendly”.