trooper sean cullen NJSP headshot

NJSP Trooper Sean Cullen was killed in March 2016 when he was hit by a car while investigating a car fire on I-295 in Deptford. (New Jersey State Police photo)

New Jersey State Police were curious how a photo of fallen trooper got on the set of "It's Always Sunny in Philadelphia."

It appears the gang simply asked the trooper's family for it.

The pic of Trooper Sean Cullen can be seen hanging behind in Paddy's Pub -- the show's main setting -- in "A Cricket's Tale," the ninth episode of the recently concluded 12th season.

Case closed! On Monday we posted this pic, which is a still from the television show, "It's Always Sunny in... Posted by New Jersey State Police on Friday, March 24, 2017

The 31-year-old Cullen was fatally injured a year ago when he was hit by a vehicle while responding to a car fire in South Jersey.

"According to Sean's family, the show contacted them and asked permission to use the photo!" state police said in a Facebook post on Friday, following up a post earlier in the week wondering how Cullen's face got behind the bar.

Some of Cullen's family also got to play extras in the episode, state police said.

"Well, played 'It's Always Sunny in Philadelphia,' well played," the post concluded.

Steve Novak may be reached at snovak@lehighvalleylive.com. Follow him on Twitter @type2supernovak and Facebook. Find lehighvalleylive.com on Facebook.