Here is West Yorkshire Police's full statement following the murder of Batley and Spen MP Jo Cox.
Temporary Chief Constable of West Yorkshire Police Dee Collins said: "Just before 1pm today, Jo Cox, MP for Batley and Spenborough was attacked and fatally wounded on Market Street Birstall.
"Before going into further detail, I would like to express our deepest sympathies to her family and friends at this tragic time.
"Jo was attacked by a man, who inflicted serious and sadly, ultimately fatal injuries. Subsequently there was a further attack on a 77-year-old man, nearby who has sustained injuries that are non life threatening.
"Shortly afterwards, a man was arrested nearby by uniform police officers. Weapons including a firearm have also been recovered.
"At 1.48pm, Jo Cox was pronounced deceased by a doctor working with a paramedic crew that was attending to her serious injuries.
"This is a very significant investigation with a large number of witnesses that are being spoken to by the police at this time. There is a large and significant crime scene and there is a large police presence in the area. A full investigation is underway to establish the motive for this murder.
"There are specially trained officers with Jo’s immediate family who are fully aware of what has taken place. We would ask the media to respect their privacy at this time.
"We are not looking for anyone else in connection with this incident at this time."
West Yorkshire’s Police and Crime Commissioner, Mark Burns Williamson, said: "My thoughts and prayers are with Jo’s family at this time.
"I have worked closely with Jo since she was elected and I am deeply shocked that such a talented young woman has been senselessly attacked and killed whilst working in her constituency and serving her community.
"This is a truly shocking incident but I want to reassure communities that our information is that this is a localised incident, albeit one that has a much wider impact.
"I must stress that investigations are ongoing, a man has been arrested, and we need to let the police do their job in understanding exactly what has happened that led up to this hugely tragic incident and channel all our thoughts into supporting the families and communities affected."
Police are appealing for any witnesses to the incident to contact 101.