Brian Kennedy, 37, was found guilty of first-degree murder in the death of Stephanie Miller.
It happened inside a Wawa in Radnor Township back in March 2019.
Authorities say Kennedy used an AR-15 to kill the mother of his child.
SEE ALSO: Man accused of killing ex-wife inside Radnor Twp. Wawa store
Man accused of killing ex-wife inside Radnor Twp. Wawa store
"It was horrible. One of the most horrible things that people in Radnor have seen in quite a long time," said Delaware County DA Jack Stollsteimer after the guilty verdict was reached Thursday.
Authorities say Miller was shot four times in a store full of people.
"He brought a weapon of war, came in and killed his ex-wife because he was apparently unhappy with her," said Stollsteimer.
The DA's office says Miller had a previous "protection from abuse order" against Kennedy.
A sentencing date for Kennedy was not immediately released.