The 22-year-old man was taken into custody on Friday night, police said. He is expected to be charged with attempted murder and related offenses.
Police say his name will be released once formal charges are filed.
The shooting happened around 4:45 a.m. Friday at the store in the 1300 block of E. Erie Avenue in the city's Juniata section.
Police said the incident started as an argument between a Wawa security guard and the suspect after the suspect was told he could not enter the business because it was at capacity.
A second off-duty security guard, who authorities say worked at a local club, stepped in to help and got into a physical struggle with the suspect.
The off-duty security guard, identified by family members as Khalil Patterson, was shot once in the chest, police said.
This is the victim, 25 year old Khalil Patterson. Family says he’s currently in surgery and praying he pulls through. They said he’s always willing to jump in and help other people, which is probably why he defended Wawa security guard this morning @6abc https://t.co/frQcNF0DwH pic.twitter.com/kRMkWwLEmn— Jaclyn Lee (@JaclynLeeTV) August 28, 2020
He was taken to the hospital where he is listed in critical condition.
"We're just praying for him to pull through because he's in surgery right now," said Kim Thomas, Patterson's aunt. "I feel like he was doing the right thing."
Family members describe Patterson as a father, and someone who is always willing to jump in and help others.
"Over social distancing, that's something that could be talked out. You don't have to put a gun up to anybody," said Makayla Thomas, Patterson's cousin.
One bullet was recovered at the scene, police said.
Witnesses said the suspect and an accomplice seemed intoxicated when they showed up to the Wawa.