charged with using a weapon of mass destruction. then deadly floodwaters are rising in the midwest. swallowing up homes. is there any relief in sight? plus a 6-year-old survives a horrifying alligator attack. we're going to talk to joey welch about the very moment an eight foot alligator chomped down on his arm and how he just walked away with a few scratches. john, this 6-year-old little guy, i mean, he says i told my dad, are we going to see an alligator? maybe we shouldn't do this. he's a very cute kid. i can't wait for you to see him. >> cute and lucky and brave. all right, christine romans, thanks so much. back here in boston, we are getting new details into the investigation into the alleged boston bomber dzhokhar tsarnaev. we're learning more about signs that his older brother tamerlan may have become radicalized, and when dzhokhar possibly began to follow his brother's lead. here's cnn's brian todd.