A Glendale house struck by improvised pipe bombs Wednesday morning has been the target of previous attacks, according to the Glendale Police Department.
The ABC15 Investigators learned all three cases are so similar that they are now part of the same investigation.
Police told ABC15 they could not release specific details about the cases that occurred in the summer of 2011 because they have been reopened as part of the current investigation.
A spokesperson for the Bureau of Alcohol, Tobacco, Firearms, and Explosives told ABC15 he would not reveal a possible motive for the explosions.
According to Maricopa County Assessor's records, Richard and Wanda Gray have owned the home since 1999. The Glendale Police Department will not reveal whether the homeowners were inside the house during any of the explosions.
The Deer Valley Unified School District confirmed homeowner Dr. Richard Gray has worked for the district for fourteen years. He is a psychologist who manages all of the psychologists within the district, said Heidi Vega, a spokesperson for the district.
Gray is also responsible for handling legal mediation and evaluating threats of litigation involving parents and students, according to a 2010 district description of his job duties. The district also listed formal school complaints and threat assessments as part of his duties.