adding this little tidbit about finding the shootout pressure cooker lid embedded in a car...
http://news.yahoo.com/boston-bombing-suspect-still-hospitalized-guarded-072110364.html
“We’re in a gunfight, a serious gunfight. Rounds are going and then all of the sudden they see something being thrown at them and there’s a huge explosion,” Watertown Police Chief Edward Deveau said Saturday of the melee.
The chief said one of the explosives was the same type used during the Boston Marathon attack, and authorities later recovered a pressure cooker lid that had embedded in a car down the street. He said the suspects also tossed two grenades before Tamerlan ran out of ammunition and police tackled him.