New details emerged Friday afternoon in the mass murder-suicide that has Missouri police investigating multiple crime scenes across Texas County.

A total of seven people were discovered shot to death at four separate residences between Thursday night and Friday morning, police told USA Today. Another fatality, a woman in her 70s, was also discovered, while police were canvassing the area where the murders took place in the small community of Tyrone, Mo. Highway Patrol said.

The woman reportedly had no signs of trauma and is believed to have died from an illness.

Investigators are saying the 36-year-old gunman is the son of the elderly woman, the St. Louis Post-Dispatch reported. It appears that when the son found his mother dead, he left and went door-to-door shooting people before killing himself.

"We're speculating that he came home and found her deceased and then for whatever reason went on a rampage and started killing people," Texas County Coroner Tom Whittaker told the newspaper.

"This is just so strange. Right now, with the shooter dead, we don't know. Is there something that sparked this? We're still in the information gathering stage."

Whittaker also said the woman had been dead for at least 24 hours.

Investigators have withheld the names of all involved. The victims include three women and four men ranging in ages from early 40s to mid 60s, according to the Post-Dispatch. Some of the victims had the same last name as the elderly woman.

Police discovered the first of the bodies after receiving a call from a terrified girl on Thursday night. The child reported hearing gunshots "and immediately fled to a neighbor's house," police said according to USA Today.

Two bodies were found at the girl's residence in Tyrone, an unincorporated community. Five more bodies and an injured victim were found at three more residences.

After the murders, police believe the shooter drove to neighboring Shannon County and shot himself. His body was found in the car.

Autopsies are expected to be performed in Springfield, Mo., officials told the Post-Dispatch.