. >>> boston police shot and killed a man under 24 hour surveillance by the fbiful he pulled a military knife when an another tried to question hip. and said he was radicalized by i.s.i.l. and watched by the u.s. joint terrorism task force. >> he was someone we watched for a time. constalent dialogue between us and the f.b.i. the level brought us to question you today. i don't think anyone expected the reaction we can get out of him. that's why we had the tragic turn over. >> there was no reason to be concerned about public safety. >> a friend of bovtom bomber dzhokhar tsarnaev has been sentenced to prison. he pleaded guilty to interfering with the investigation, he took its from the dorm room after the bombers carried out the bombings. he told the judge he was ashamed of what he did. >> in china, the fate of people in a cruise ship was unclear. 458 people were on board when the ship sank. so far there's 15 confirmed survivors. some were alive in an air pocket in the submerged hull. adrian brown filed this report. >> reporter: behind me the yangtze river, a powerful symbol in this part