Amess, 69, was knifed repeatedly in the attack at about midday Friday (October 15) in Leigh-on-Sea, east of London.
Mourners described him as a "genuine, caring and compassionate man," as they lit candles and paid tributes to the politician.
The attack on David Amess, from Johnson's Conservative Party, comes five years after the murder of Jo Cox, a lawmaker from the opposition Labour Party, and has prompted a review of the security of elected politicians.
Police arrested a 25-year-old British man at the scene on suspicion of murder. Police have said it is believed the man acted alone.
In a statement early on Saturday, police said the early investigation had revealed a potential motivation linked to Islamist extremism. Later on Saturday, police said they were granted a warrant to detain the man until Friday before they have to decide whether to charge him.