Boston Bombs were pressure cookers hidden in backpacks - Investigators

Investigators believe the bombs at the Boston Marathon were shrapnel-studded pressure cookers, hidden in backpacks and set off by timing devices, law enforcement officials say on Tuesday.

An explosion goes off near the finish line of the Boston Marathon on April 15. Two explosions struck the marathon
as runners crossed the finish line on Monday, witnesses said, injuring an unknown number of people on
what is ordinarily a festive day in the city

The disclosure came as authorities pleaded with spectators from the race to send photos and video that may shed light on who set off the blasts, killing three people and injuring at least 176.

The top FBI official in Boston vowed to go “to the ends of the earth” to find those responsible. But a day after the explosions, President Barack Obama said authorities still did not know whether the attack was foreign or domestic, the work of a group or an individual, or what the motive might be.

Runners continue to run towards the finish line as
the second explosion detonates.

Law enforcement officials told reporters that the explosives were classified as low — meaning that they traveled at under 3,300 feet per second. That is not enough to create a blast wave, which can kill people from air compression and blow out faraway windows, but it is enough to propel shrapnel a great distance.

A pressure cooker, in its everyday use, speeds cooking by creating a tight seal and building pressure inside the pot. Converting it to a bomb sheaths the explosives in a metal casing, which blows apart when the bomb is detonated and adds to the shrapnel already packed inside.

In 2010 the pressure cooker was one of the three devices that was to be used in an attempted bomb attack in Times Square. In the Boston bombings, informal public efforts sprang up almost immediately to scour the mass of photos and video already posted on Twitter, Facebook and other sites for clues. Authorities added their own call for help, hoping that in an era of ever-present smartphones, race fans might be holding evidence without even knowing it.“There has to be hundreds, if not thousands, of photographs, videos and other observations that were made down at that finish line yesterday,” said Timothy Alben, superintendent of the Massachusetts State Police. “You might not think it’s significant, but it might have some value to this investigation.”

So go ahead and load those pictures and videos if you have any.