In this photo made on marathon weekend and made available by Brian Gross shows his sister-in -law Nicole Gross, right, with her mother Carol Downing. Nicole Gross, and her husband Michael Gross of Charlotte, N.C. were seriously injured when two bombs exploded near the finish line of the Boston Marathon Monday, April 15, 2013. The Gross couple and Nicole's sister, Erica Brannock of Maryland, who was also injured while cheering Downing, who was running the race. Downing was not injured. (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.