Conservative MP Sir David Amess has died following a stabbing at a constituency surgery held in his Southend West.
A 25-year-old man was arrested at the scene on suspicion of murder, as police said the knife used in the attack was recovered by officers.
The 69-year-old was attacked on Friday at Belfairs Methodist Church in Leigh-on-Sea.
Prime Minister Boris Johnson lead the tributes to his Conservative colleague as he described the man as “one of the kindest, nicest most gentle people in politics”.
"David was a man who believed passionately in this country and in its future and we have lost today a fine public servant and a much-loved friend and colleague,” Mr Johnson added.
"Our thoughts are very much today with his wife, his children and his family.
“I think everybody was deeply shocked and heart stricken. We must really leave the police to get on with their investigation.”
The father-of-five is the second sitting MP to be killed in such circumstances in five years, following the death of Labour MP Jo Cox in 2016 as she attended a constituency surgery.
Witnesses described the scene as "very distressing" as Sir David was treated by emergency services at the scene before passing away as a result of his injuries.
Essex Police said: "A man has been arrested on suspicion murder after a man was stabbed in Leigh-on-Sea.
"We were called to an address in Eastwood Road North shortly after 12.05pm today (Friday 15 October).
"We attended and found a man injured.
"He was treated by emergency services but, sadly, died at the scene.
"A 25 year-old man was quickly arrested after officers arrived at the scene on suspicion of murder and a knife was recovered.
Devastated to learn of Sir David Amess' murder. A great man, a great friend, and a great MP killed while fulfilling his democratic role.— Sajid Javid (@sajidjavid) October 15, 2021
My heart goes out to Julia, his family, and all who loved him.
Let us remember him and what he did with his life.
"He is currently in custody.
"We are not looking for anyone else in connection with this incident."
Sir David, 69, had been an MP since 1983 and was married with five children.
Terrible day with the loss of Sir David Amess MP, a victim of dreadful crime. Democracy will not be defeated by such barbarity. Our prayers and thoughts are with his family and friends at this dreadful time— Peter Weir (@peterweirmla) October 15, 2021
Prime Minister Boris Johnson has arrived back at Downing Street on Friday afternoon from Bristol where he had been holding a cabinet meeting.
The speaker of the House of Commons Sir Lindsay Hoyle confirmed flags across Parliament are being flown at half mast in tribute to the MP.
Flags across Parliament are being lowered to half-mast following the news of the killing of Sir David Amess. Our thoughts and prayers are with David’s family, friends and colleagues. pic.twitter.com/0LDI8E5NpU— Sir Lindsay Hoyle (@CommonsSpeaker) October 15, 2021
Flags at Downing Street are also flying at half mast in tribute.
The first floral tribute has been laid at a police cordon set up at the scene of the murder.
The tribute, laid by a young woman, read: "A silent thought, a quiet prayer, for a special person in God's care. May you rest in peace."
The cordon is still being manned by Essex Police as forensic officers carry out their investigations, which started after the Conservative MP was stabbed at around lunchtime on Friday.
Tributes have also been paid across the political spectrum.
Former Conservative prime minister Theresa May tweeted: "Heartbreaking to hear of the death of Sir David Amess.
"A decent man and respected Parliamentarian, killed in his own community while carrying out his public duties. A tragic day for our democracy. My thoughts and prayers are with David's family."
Her predecessor David Cameron also paid tribute to the Southend West MP.
David Cameron wrote online: “This is the most devastating, horrific & tragic news. David Amess was a kind & thoroughly decent man - & he was the most committed MP you could ever hope to meet.
"Words cannot adequately express the horror of what has happened today. Right now, my heart goes out to David’s family.”
Scottish First Minister Nicola Sturgeon said: "Elected representatives from across the political spectrum will be united in sadness and shock today.#
Sir John Major added: “This is truly heartbreaking news of a good and decent man who - for over 30 years - was a dedicated public servant.
"My heart goes out to his family."
"In a democracy, politicians must be accessible and open to scrutiny, but no-one deserves to have their life taken while working for and representing their constituents."
Welsh First Minister Mark Drakeford added: "Deeply saddened to hear about the death of Sir David Amess. A truly despicable and horrifying act.
"My thoughts are with his friends, family, and constituency staff during this distressing time."
Liberal Democrat leader Sir Ed Davey said: "This is tragic and horrible news. My thoughts are with David's wife and children, the wider family, friends and David's community.
"A truly terrible day for British politics but most importantly of all our prayers are with all the people who loved David."
Scottish National Party MP Mhairi Black said: “Just the most horrific news. To hear of a public servant being attacked whilst carrying out his duty in his constituency is simply heartbreaking. My thoughts are with his family and loved ones.
“Surgeries are a critical part of an MPs work. They are a place where people speak about the most personal of struggles. They should be a safe place for everyone, including politicians and their staff.”