▶ Watch Video: CBS News Boston

The suspect in the mass shooting that killed 18 people in Lewiston, Maine, has been found dead, multiple law enforcement sources confirmed to CBS News Friday.

It was not immediately clear where 40-year-old Robert Card’s body was found, or his cause of death. A news conference was scheduled for 10 p.m. ET Friday night. 

Hundreds of state and local police and federal agents have been involved in the manhunt since the shootings Wednesday night. There was an arrest warrant out for Card on murder charges, police said. 

For several hours Thursday night, heavily armed police had surrounded a house in Bowdoin, a small college town where Card is from, about 35 minutes from Lewiston, but they completed their search there without finding him. 

On Friday, police announced divers were conducting underwater searches near a location where Card’s vehicle, a white Subaru Outback, was found abandoned by a boat launch on the Androscoggin River. 

Authorities had recovered a weapon from the suspect’s abandoned vehicle, law enforcement sources told CBS News’ Pat Milton and Robert Legare earlier Friday. The firearm was legally purchased, a law enforcement source confirmed. It wasn’t clear if the recovered weapon was used in the shooting.

CBS News had also learned that investigators had located Card’s cellphone and were trying to crack it and pore over his online activity, including text messages and emails, hoping to find clues as to his motive in the shootings.

The deadly rampage began a little before 7 p.m. Wednesday night, when police received a 911 call about a shooting at Sparetime Recreation, a bowling alley in Lewiston. Police later said six males and one female there died of apparent gunshot wounds. 

Just over 10 minutes later, at 7:08 p.m., police were called to the scene of another shooting a few miles away, at Schemengees Bar and Grille. Eight people there were killed, police said. Three other people died at area hospitals.

Police said the gunman fled in the aftermath of the shootings and they warned that he “should be considered armed and dangerous.”

Card, a member of the U.S. Army Reserve, had recently reported experiencing mental health issues, including hearing voices, and threatened to shoot up a military base in Saco, a law enforcement bulletin seen by CBS News said. In July, Card started “behaving erratically,” a New York Army National Guard spokesperson told CBS News, and he was committed to a mental health facility for two weeks.

About 80 FBI agents were working with state and local law enforcement in the search, Senator Susan Collins said at a news conference Thursday evening. 

Several communities in the area have spent the days since the shooting under shelter-in-place warnings, with schools canceled and residents urged to stay indoors. 

“For me it was incomprehensible that this can happen in Lewiston, Maine,” Mayor Carl Sheline told CBS News Boston.

“Our city is facing this incredible loss and I am completely broken for our city, and my heart really goes out to the victims and their families right now,” Sheline said.

Investigators were looking into whether the suspect may have been targeting a specific individual, who is believed to be a current or former girlfriend, two U.S. officials and a former high-ranking official told CBS News. It wasn’t clear if she was at either of the two locations that were attacked.

The victims of the mass shooting ranged in age from 14 to 76, the medical examiner said. They included a bar manager who tried to stop the gunman; a bowling instructor who was teaching kids; a beloved father; a 14-year-old and his dad; and several people taking part in a cornhole tournament for deaf athletes.

Jeff Pegues, Andres Triay, Robert Legare and Matthew Mosk contributed to this report.