Hundreds of people came together to hold a vigil for MP Jo Cox, who was killed yesterday in Birstall, West Yorkshire.
Jo worked as a Member of Parliament for the Labour party representing the Batley and Spen area in Yorkshire.
On Thursday, Jo was attacked and killed near to where she had been holding a constituency surgery, where local people can talk to her about any problems they have.
A local man has been arrested.
The Prime Minister David Cameron has said: "The death of Jo Cox is a tragedy. She was a committed and caring MP."
It's very rare that these kinds of attacks happen in the UK.
BBC Reporter John Maguire sent us this report from Birstall in Yorkshire.