This undated photo made available by Brian Gross shows his sister-in-law Nicole Gross, and brother Michael Gross of Charlotte, N.C. The Gross couple were seriously injured when two bombs exploded near the finish line at the Boston Marathon Monday, April 15, 2013. Nicole's sister, Erica Brannock of Maryland, who was also injured, were cheering their mother, who was running the race. (AP Photo/courtesy of Brian Gross)
Gallery: More photos from Boston explosion
Apr. 16, 2013 @ 01:16 PM
Investigators believe the two bombs that ripped through the crowds at the Boston Marathon, killing three people and wounding more than 170, were fashioned out of pressure cookers and packed with shards of metal, nails and ball bearings.