A grandfather shot dead his daughter and her six children before taking his own life at a home in Bell, Florida, police have said.
The children range in age from 3 months to 10 years old, said Gilchrist County Sheriff Robert Schultz.
The authorities have identified the gunman as Don Charles Spirit, 51.
Police have said they received a call from Spirit making threats to his family and himself before he committed suicide.
"I haven't seen anything like this at all," said Schultz.
"This county, this community is going to be devastated from this. It is a small county, we are all family here.
"We're asking for prayers for this community and the families involved."
Schultz said a colleague responded to reports of a shooting on Thursday afternoon and spoke to Spirit before the man committed suicide.
Police then found the other seven bodies in the house, although there were other people still alive there.
Spirit, who was known to police previously, was the only suspect, said Schultz.