Za Uk Lian, 45, shot at a woman on Route 22 in Upper Macungie Township shortly before 5 a.m. She was not injured.
He then pulled into a Wawa parking lot where he shot and wounded a man in a Jeep, then shot and killed a truck driver who was pumping gas.
Lian then walked down the road where he shot and killed himself.
On Thursday, District Attorney Jim Martin said Lian purchased the .40 caliber semi-automatic pistol legally in January.
Lian applied for a concealed carry permit in February and received approval last month.
There is still no word on a motive.
The truck driver who was killed, 31-year-old Ramon Ramirez of Allentown, was a father of three.