• Boston and the neighboring towns of Belmont, Cambridge, Newton, Waltham and Watertown are on lockdown as police seek the second of two Chechen brothers suspected of committing Monday’s attacks at the Boston Marathon. The elder of the two was killed early Friday in a shootout with police after the pair fatally shot an MIT campus police officer. [Boston Globe]

• The dead suspect has been identified as 26-year-old Tamerlan Tsarnaev, who maintained a YouTube page where he posted extremist Islamic religious videos, including an end-of-days prophecy also promoted by members of al Qaeda. [Mother Jones]

• The suspect at large has been identified as Dzhokhar Tsarnaev, a 19-year-old who received a Cambridge city scholarship in 2011.

• After a year of secret negotiations, the Pentagon is on the verge of finalizing a $10 billion arms deal with Israel, Saudi Arabia and the United Arab Emirates intended to maintain American allied military superiority over Iran. [NYT]