Boston Marathon bombing investigation extends to Russia

Wednesday, April 24, 2013 | 7:13 p.m. CDT; updated 9:59 a.m. CDT, Thursday, April 25, 2013

BOSTON — From Boston and Washington to Russia, investigators pressed for answers Wednesday about the Muslim radicalism believed to be behind the Boston Marathon bombing, while more than 4,000 mourners paid tribute to a Massachusetts Institute of Technology police officer who authorities say was gunned down by the bombers.