Maine shooting: New details emerge in Robert Card's death

The family of mass shooting suspect Robert Card is cooperating with authorities, law enforcement officials briefed on the investigation told ABC News.

The family is laying out an account of a deeply troubled person, the sources said, bolstering earlier accounts of mental health treatment, voices in his head and alleged threats to shoot up a National Guard facility.

Card's sister told investigators she thought Card might have been looking for an ex-girlfriend at the shooting locations: a bowling alley and a bar, the sources said.

The U.S. Coast Guard is searching the Kennebec River in Maine for any sign of the mass shooting suspect, Robert Card.

Card owns a boat and property in the Lewiston area, according to a source briefed on the situation.

"Currently, one response boat crew from Station Boothbay Harbor, and an Air Station Cape Cod HC-144 fixed wing aircraft are assisting with patrols," Coast Guard spokesperson Rob Simpson said in a statement.

Maine mass shooting suspect Robert Card allegedly behaved erratically this summer while serving as an Army reservist, according to a defense official.

Card was deployed to Camp Smith Training Center in upstate New York to help support summer training for West Point cadets.

Card allegedly threatened other soldiers with violence, according to a source briefed on the situation.

"Out of concern for his safety, the unit requested that law enforcement be contacted," the defense official said. Police took Card to Keller Army Community Hospital at the United States Military Academy for a medical evaluation, the official said.

Sometimes this spring or summer, Card bought an accessory to a firearm, according to the source briefed on the situation.

With the manhunt for Card ongoing, the source noted that Card owns a boat and property in the Lewiston area.

-ABC News' Luis Martinez and Pierre Thomas

A sweeping dragnet effort is underway on the ground and in the air as law enforcement partners fan out in full force in their search for the suspected Lewiston gunman, Robert Card.

More than 350 law enforcement personnel are involved in the search.

Evidence response teams are already on the ground, processing the "very extensive scenes" where the shootings took place, FBI Special Agent in Charge Jodi Cohen said.

In these early stages, investigators are probing potential mental health issues Card may have had, and how he was in possession of a weapon.

5:07

Multi-agency manhunt continues for Maine shooting suspect

ABC News contributor Brad Garrett discusses what federal and local law enforcement is doing to capture the suspect in the fatal Lewiston mass shooting.

ABCNews.com

A motive has also not been determined.

"I think those are all valid questions and certainly questions that we are looking into now, but not questions that we can answer today," Commissioner of Maine's Department of Public Safety Mike Sauschuck said.

-ABC News' Sasha Pezenik