Police say a gun went off at about 11 p.m. Saturday at the Cathedral of the Blessed Sacrament in Altoona, Blair County.
Jason Wagler was sitting with his fiancee at Mass and heard the gunshot.
"We were standing for a few minutes and just before the final procession started, the gunshot went off," Wagler said.
Wagler said at first no one seemed to know what had happened. Some people thought a speaker blew. But then he saw smoke. Wagler took several photos with his phone shortly after the incident happened.
"I immediately took a step back and was about to take cover. You never know if you're safe anymore in this world. It's a shame to know you can't go into church without having something like this happen," Wagler said.
Police say a man had a gun in his pocket and it discharged when he stood up. The bullet grazed the man's hand.
An Altoona newspaper reported the trigger caught on the man's pants and the gun's safety was not on.
"I noticed the gun was handed to another gentleman. He immediately concealed it in a white program, so I took pictures of the gun inside this program," Wagler said.
The man was taken to the hospital. Police haven't released his name.
It's unclear why he brought a gun into church. At this point, no charges have been filed.