Kate McCann, whose daughter Madeleine was abducted in Portugal in 2007, says she has not been put off competing in the London marathon by the Boston bombings.
She is an ambassador of the Missing People charity and is aiming to raise £20,000 to mark its 20th anniversary.
"This sickening act is just incomprehensible and the loss of life, especially that of a young child, heart-breaking.
"But I feel strongly that you can't live in fear or you don't have a life."
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West Midlands Police are hunting a driver of a car who mounted the pavement and ploughed into a 17-year-old girl in front of her mum.
Birmingham City Council have started chopping down the city's oldest tree despite campaigns to save it.
A man convicted of preparing to commit acts of terror has today pleaded guilty to possessing a hand-written bomb making recipe in prison.