"Basically, there were two roommates there," Cummings said. "They said, 'We saw him yesterday and he was fine.'"
He told Ciancia's father that because of his son's age, he couldn't take a missing persons report.
Authorities say Ciancia pulled a semi-automatic rifle from a bag and shot his way past a security checkpoint at the airport, killing a security officer and wounding other people. Ciancia was injured in a shootout and taken into custody, police said.
A motive wasn't clear, but Ciancia was wearing fatigues and carrying a bag containing a handwritten note that said he "wanted to kill TSA and pigs," according to a law enforcement official who was not authorized to discuss the investigation publicly and spoke on condition of anonymity.
The Pennsville Police Department has had no dealings with the younger Ciancia, Cummings said. He and neighbors described the Ciancias as a good, nice family.
Ciancia graduated in 2008 from Salesianum School, an all-boys Roman Catholic school in Wilmington, Del., across the Delaware River from Pennsville, the school said.
The suspect's father has been involved with Pennsville's Fraternal Order of Police, said neighbor Orlando Pagan, a lieutenant in nearby Penns Grove. He didn't provide details on his involvement.
Outside the father's home Friday in Pennsville, a police cruiser blocked the long driveway. Phone calls weren't answered, and efforts to reach siblings were also unsuccessful.
Orlando Pagan's 17-year-old son Josh said that he would sometimes encounter Ciancia at orthodontist appointments, but that it had been at least two years since the last one.
"He was never weird toward me. He never gave me any weird vibes," he said, adding that in the 10 years he has lived across the street from the Ciancia family, "they've been nothing but nice to us."