Police don't know why Postreich allegedly crossed the property line and went after his neighbor.
Both men are 70 years old.
After the multiple hits from the hatchet, police say the victim fought back.
"Neighbor grabbed him by the mask, it came off and he identified him," Ripper said.
Police served a warrant at Postreich's home on Thursday.
Investigators told WPXI they were looking for a stun gun because the victim told police Postreich tried to shock him with one.
WPXI has learned the neighbors have been in civil court before and are known to police, but this is the first criminal investigation.
"They've had problems for years, don't know what sparked this," Ripper said.
WPXI contacted the victim, but his attorney told him not to talk.
He did say he thought he was going to die during the attack.
The district attorney is reviewing this incident to see if they should amend the assault charges to attempted homicide.