A man was killed and a Liberal Democrat MP was wounded by a man wielding a sword, at a constituency office in Cheltenham, Gloucestershire, last night.
The local MP, Mr Nigel Jones (51), was slashed and his aide, named locally as Lib Dem councillor and school governor Mr Andrew Pennington, was stabbed to death at the party's office in St George's Street, Cheltenham.
Mr Jones, married and a father of three, was taken to hospital and treated for lacerations to his hands. His condition was not life-threatening, but he was expected to stay in hospital overnight.
Police arrested a 49-year-old Cheltenham man 10 minutes after being alerted.
The Liberal Democrat leader, Mr Charles Kennedy, described the attack as "a wicked act".
He said, "This is an appalling and senseless tragedy and my heart goes out obviously to the colleague who has lost his life, as well as to Nigel Jones, my parliamentary colleague . . .
"It is an affront on the parliamentary process. MPs can't conduct their lives in glass boxes, hermetically sealed from their constituents. Equally, their constituents have got every right to come and see all of us, from all parties, in all parts of the country, knowing that they are going to be safe and secure in so doing."
Neighbours described Mr Pennington as a "good Samaritan figure" who would go out of his way to help those in the community.
Mr Nigel Davies (50), who lives just doors away from Mr Pennington on Hesters Way Road, Cheltenham, said: "He was a fine, fine man, dedicated to his work, especially when local elections were coming up. It's just tragic."
The attack took place at 4.30p.m., and an ambulance was called two minutes later.
Eye witnesses said they saw a tallman brandishing what looked like a samurai sword going into Mr Jones's surgery. One said the man appeared to go "crazy".
Cheltenham borough councillor Mr Brian Cassin said Mr Jones had been dealing with a difficult caseload involving the alleged attacker.
In a statement the Home Secretary, Mr Jack Straw, said: "I share the deep sense of shock that everyone will feel at the death of Nigel Jones's assistant following this horrific attack. We send our deepest sympathy to his family and colleagues."
Mr Jones won the Cheltenham seat in 1992. At the last election, he had a majority of 6,645. He moved into full-time politics following a career as a computer programmer and systems analyst.