DHS Police in Airports

Earlier this year I flew out of Philadelphia and noted DHS Police in the terminal near the gates, just sort of standing/walking around as if on patrol. It struck me as odd but I don’t fly that often and shrugged it off. I’ve seen Federal Protective Services Police in Philly at the U.S. Mint and other federal buildings but never at an airport. According to Wikipedia, the DHS Police are a protective service for buildings owned or operated by the federal government. How does this translate into patrolling an airport? Also, it appears that they can only enforce federal laws, which makes sense. But for more routine police work (drunks, thefts, disorderly etc.) that don’t impact air operations directly, the local police have to be called. Philly PD already has an airport unit so why DHS?

Never mind - obviously, the airport is occupied by hundreds of federal employees, the protection of whom is part of their duties.