Oct. 26 (UPI) -- Police late Thursday continued to search for the suspect in a pair of mass shootings that left at least 18 dead and 13 injured in Maine on Wednesday, and authorities continue to advise residents to shelter in place.
Police swarmed the house of Ryan and Katie Card, the brother and sister-in-law of the suspect, Robert Card, 40, who is wanted on eight counts of murder in the shootings in Lewiston.
Using a megaphone, officers shouted, "Robert Card, you're under arrest. Come out now," according to a report by ABC News, which said officers remained uncertain if Robert Card was inside the home.
"It is unknown whether Robert Card is in any of the homes law enforcement will search," said Shannon Moss, a spokeswoman for the Maine State Police. "Law enforcement officials are simply doing their due diligence by tracking down every lead in an effort to locate and apprehend Card."
Residents of two counties have been told to stay inside and lock their doors.
"It's a tactical operation," Moss said.
More than 350 state and federal law enforcement officials are searching by land, air and sea for Robert Card.
The Hannaford supermarket chain, a major Northeast grocer, said it has closed all 58 of its stores in accordance with the shelter-in-place order.
As the manhunt continued Thursday, Portland city officials closed all public buildings except for City Hall and its health department.
The Portland International Jetport remained open.
Police have yet to share details about where they are searching for Robert Card, the suspect in the most deadly mass shooting in the United States this year, and potentially the deadliest in Maine's history.
Robert Card, a resident of Bowdoin, is a trained firearms instructor who police believe is in the U.S. Army Reserve. According to a spokesperson for the Army's Office of the Chief of Public Affairs, Card has served in the reserves for more than 20 years and has earned several medals, including the Army Achievement Medal and the Humanitarian Service Medal, the Portland Press Herald said.
Gov. Janet Mills updated the death toll on Thursday morning, and offered condolences to the families of the victims.
"This is a dark day for Maine," Mills said. "I know it's hard for us to think about healing when our hearts are broken but I want every person in Maine to know that we will heal together. We are strong, we are resilient, we are a very caring people."
Seven people were killed at Just-In-Time-Recreation, and eight of the victims were found dead at Schemengees Bar & Grille in Lewiston.
Three people died after being taken to local hospitals.
President Biden released a statement Thursday offering support while asking residents of the area to follow the directions of local officials.
"Once again, our nation is in mourning after yet another senseless and tragic mass shooting," Biden said. "Today, Jill and I are praying for the Americans who've lost their lives, for those still in critical care, and for the families, survivors, and community members enduring shock and grief."