Philadelphia Police, the Bureau of Alcohol, Tobacco and Firearms and the U.S. Postal Service are investigating the explosion.

A device hidden inside a package exploded and injured a man in his Center City apartment around 4 a.m. on Tuesday, 6abc Action News reported.

According to 6abc, the explosive device was hidden inside a manila envelope and was triggered when the victim, a 60-year-old man, opened it.

“The bomb squad says no question it was targeted,” Philadelphia Police Commissioner Richard Ross told 6abc. “It was addressed to him. They do not believe it was mailed. They believe it was placed there. The reason they believe that is because the bar code was old, and it would not have gone through the U.S. mail.”

Philadelphia Police, the U.S. Postal Service and the Bureau of Alcohol, Tobacco and Firearms are investigating the explosion.

All comments eligible for publication in Daily Pennsylvanian, Inc. publications.