Sep 5, 2012 7:34 PM by AP
PHOENIX (AP) - Federal authorities are investigating a pipe bomb explosion in front of a Glendale home, the third incident at the address in less than two years.
Glendale police said nobody was injured in the explosion early Wednesday although shrapnel punched through the home's garage roof, stucco wall and the garage door.
A spokesman for the Bureau of Alcohol, Tobacco, Firearms and Explosives says the pipe bomb detonated between two cars and was powerful enough to kill someone.
The Arizona Republic says police don't believe the latest explosion is random and Glendale police explosive ordinance experts and federal ATF agents are investigating it.
Police are baffled at why the residents of the home have been targeted. Their names haven't been released, but one resident is a Deer Valley School District employee.