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 of Yorkshire.
On Thursday, Jo was attacked 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."
Jeremy Corbyn, who is the head of the Labour party that Jo worked for, has said that she was a, "much loved colleague, a real talent and a dedicated campaigner for social justice and peace".
Jo worked with charities around the world and in the UK to help tackle poverty and discrimination.
It's very rare that these kinds of attacks happen in the UK.