West Yorkshire Police have called a press conference in which they announced that the Labour MP Jo Cox has died of injuries sustained in an attack in her constituency.
Here is the statement of West Yorkshire Police's chief constable, Dee Collins, in full:
"Just before 1pm today, Jo Cox was attacked in Market Street, Birstall.
"I am now very sad to report that she has died as a result of her injuries.
"I would like to express our deepest sympathies to her family and friends at this 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 sustained injuries that are non life-threatening.
"Shortly afterwards, a man was arrested nearby by local uniformed police officers.
"Weapons, including a firearm, have also been recovered.
"At 1.48pm Jo Cox was pronounced deceased by a doctor who was working with a paramedic crew that were attending to her serious injuries.
"This is a very significant investigation with large numbers of witnesses that are being spoken to by police at this time, and there is a large police presence in the area.
"A full investigation is underway to establish the motive of this attack.
"There are specifically trained officers with Jo's immediate family who are fully aware of what has taken place, and we would ask the media to respect their privacy at this very difficult time.
"Additional officers are working this afternoon and evening in order to provide reassurance to our communities.
"Clearly as this inquiry is at a very early stage and we have an individual under arrest, we are not in a position to discuss any motive at this time.
"We are not looking for anyone else in connection to this incident at present."