According to the informants, the circumstances indicate that the suspected shooter committed suicide.
The two mass shootings took place at a bowling alley and a popular bar in Lewiston, Maine, early Wednesday evening, local time.
In addition to the 18 dead, several injured are still being treated in hospital.
The suspected shooter has been described as a 40-year-old reservist and weapons instructor who had mental health problems. He was named shortly after the crime and then wanted.
Police at both the local and federal level said they were conducting “huge” efforts in the hunt for the man. Residents in the Lewis area were asked to stay indoors in connection with the incident, an advisory that was lifted Friday night.
There are still several question marks surrounding the shootings, including whether there was a motive. Last Thursday, the police searched a house belonging to a relative of the 40-year-old. According to media reports, they were looking for items such as computers, notes, weapons and other types of evidence that could point to the suspect planning the crime.
Until September 17, 501 shootings had occurred in which at least four people, excluding the shooter, were killed or injured in the United States, according to a compilation from the media company Axios. Last year, there were a total of 645 mass shootings, according to Axios.