In a news release, the Butler Township Police Department identified the victims as Clyde Knox, 82, Eva Knox, 78, Sarah Anderson, 41, and Kayla Anderson, 15.
Marlow was living in the neighborhood where the deadly shooting took place at a home his parents owned on Haverstraw Avenue, WHIO-TV reports.
After the fatal shooting, Butler Township police said they were made aware of a social media video Marlow posted. In the video, Marlow said he believed his family was "operated on with mind control," the Butler Journal-News reports.
The FBI said Marlow was charged with four counts of aggravated murder and unlawful flight to avoid prosecution.
Marlow will reportedly be extradited back to Ohio. The investigation remains ongoing.
According to Montgomery County Court records obtained by WHIO, Marlow has a criminal past, including a 2020 burglary and aggravated menacing conviction. He was reportedly sentenced to five years of probation, but that was dropped in February after a judge ruling.