It happened on Monday around 6:50 p.m. inside the Spencer Reid American Legion Post, which is located on Simpson Road.
Police say a 26-year-old man was shot one time and taken to an area hospital in critical, but stable condition.
The victim was targeted following an earlier disturbance at the Post, according to investigators.
As the suspect and another individual fled the scene, police say another man exited the Post and fired several gunshots at the fleeing vehicle.
It's still unclear if anyone inside the vehicle was hit by gunfire, and police are still trying to identify the second shooter.
An arrest warrant has been issued for 35-year-old Andrew McCutchen, of Philadelphia. He is wanted on charges of attempted homicide and related offenses. He should be considered armed and dangerous, police say.
Investigators are also searching for a dark gray 2005 Chevrolet Trailblazer LS with Pennsylvania registration MMN-9443. The vehicle has a bumper sticker to the right of the registration plate that reads "Rest Awhile Ride For Miles."
Action News spoke with a man who lives near the Post and said police were still on the scene when he returned home.
He also said he counted at least eight bullet casings in the street.
"It's pretty much chaos every other night," the man said. "It's mostly loud music but last night it took a turn for the worse."
The Memorial Day shooting has neighbors on edge.
"We heard a bunch of sirens go by and it was kind of constant for about 10 minutes maybe," noted Kelly Magri from Ardmore.
Many are also saying they're concerned over who comes and goes at the Post.
"It's supposed to be a club for veterans and I don't know who comes but it's not veterans," the man said.
Anyone with information is asked to call Lower Merion police at 610-649-1000.