Police were called to the trailer in Accomack Thursday evening because of a report of an attempted suicide, WTKR-TV, Virginia Beach, Va., reported.
The identities of the victims and cause of their death had not been released late Friday.
Omar Colon Matias told WTKR they included his sister, a friend who had been sharing the trailer with her and his niece and nephew. He said his brother-in-law, who was embroiled in a custody dispute with his estranged wife, was also among the dead.
"They treat me good, like a family member and it's kind of terrible, kind of terrible," a neighbor told the TV station.