CNN — The suspect in the Maine mass shooting started making statements about hearing voices and wanting to hurt fellow soldiers while serving at a military base this summer, and spent a few weeks in a hospital, law enforcement officials told CNN.

But a relative of the suspect and two former colleagues in the Army Reserve told CNN they weren’t aware of him having any longstanding history of mental health issues – although one former colleague remembered him as a skilled marksman and outdoorsman who was among the best shooters in his unit.

Robert R. Card II, who police are searching for in connection with the fatal shooting of at least 18 people in Lewiston, Maine, made his troubling statements while he was at the Camp Smith training facility in New York, the law enforcement officials said. His command referred him to a military hospital, and he spent a few weeks under evaluation, they said.

In July, Army Reserve officials reported Card for “behaving erratically,” and he was transported to the nearby Keller Army Community Hospital at the United States Military Academy for “medical evaluation,” a National Guard spokesman told CNN.

“Out of concern for his safety, the unit requested that law enforcement be contacted,” said the spokesperson, Col. Richard Goldenberg. New York State Police responded and transported Card to the hospital, he said.

Card then spent a few weeks under evaluation at the hospital, the law enforcement officials said.

The 40-year-old Card also threatened to shoot up a National Guard base in Maine, law enforcement officials previously told CNN.

Card’s sister-in-law, Katie O’Neill, said in a brief conversation with CNN Thursday that Card does not have a long history of mental health struggles.

“This is something that was an acute episode. This is not who he is,” O’Neill said. “He is not someone who has had mental health issues for his lifetime or anything like that.”

Except for an arrest in 2007 for an alleged driving under the influence charge, the suspect is not known to ATF or in FBI holdings, according to law enforcement sources. He legally possesses multiple weapons and owns a home on hundreds of acres of land in Maine, the sources said.

Card is a petroleum supply specialist in the Army Reserve and first enlisted in 2002, according to records provided by the Army on Thursday. He has no combat deployments, according to the records.

Clifford Steeves of Massachusetts told CNN he knew Card when they served in the Army Reserve together, starting in the early 2000s until about a decade ago. He said he never witnessed any concerning behavior from Card.

“He was a very nice guy – very quiet. He never overused his authority or was mean or rude to other soldiers,” Steeves said. “It’s really upsetting.”

Steeves said the two served together around the country at different points, including in Wisconsin, Georgia and New York. He said he felt as though he “grew up” with Card because they entered the Army as young men and trained together.

Steeves said that while “aggressive leadership was very prominent” in the Army, Card stuck out for being a “rational, understanding person” who “led through respect rather than fear.”

 Steeves said Card never saw combat but had extensive training, including firearms training and land navigation, “so he would be very comfortable in the woods.” He described Card as an “outdoors type of guy” and a skilled marksman who was one of the best shooters in his unit.

Another former Army Reserve member who served with Card also described him as a “nice guy” who “never had an issue with anybody.” The servicemember, who asked to speak anonymously due to the sensitivity of the situation, did not recall Card showing any kind of violent behavior.

Card studied engineering technology at the University of Maine between 2001 and 2004 but did not graduate, Eric Gordon, a university spokesperson, told CNN.

Public records show addresses for Card in Bowdoin, Maine, a town near Lewiston. Card appears to have been a member of a local horseshoe-throwing club in the nearby town of Lisbon, Maine, according to a local news story and a Facebook photo that showed him wearing a t-shirt with the club’s logo.

An account on the social media platform X with Card’s name and a photo that appears to be him, which has been taken offline, had a history of liking right-wing and Republican political content.

When WNBA player Brittney Griner was released from Russian detention after a prisoner exchange for a convicted arms dealer, the account posted what appeared to be its only tweet. Responding to a CNBC story about the topic, the account wrote: “Mass murderer for a wnba player great job keep up the good work,” in an apparent jab at President Joe Biden.

The account liked a tweet earlier this year from right-wing author and filmmaker Dinesh D’Souza arguing against an assault weapons ban, as well as other tweets from political figures like Donald Trump Jr. and Tucker Carlson.