Stuart Trimby from Cardiff told us how he was on the last mile of the Boston Marathon when he heard two explosions.
Pictured here with his friend Emma Clatworthy Davies before the race, he said he feels "shock and sadness" at the way a positive occasion was ruined by the explosions.
You may find some of the images in the video upsetting.
More top news
Thrifty Martin McCaskie has been using this vintage carrier for almost half his life - saves on the 5p charge!
Two families involved in supplying drugs and money laundering in north Wales have been convicted.
More rain for Wales on the way over the next few days.