Photo: The Canadian Press

Police tape marks the apartment building reported to be where Travis Reinking lives in Nashville, Tenn., Sunday, April 22, 2018.

A half-naked man suspected in the slayings of four people at a Waffle House remained on the run Monday, and authorities said he may be armed with one of the guns seized from him last year after he tried to enter the White House to see President Donald Trump.

More than 80 Nashville police officers continued to search for Travis Reinking, joined by agents with the FBI, the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives and troopers with the Tennessee Highway Patrol.

Reinking was wearing only a green jacket when he opened fire with an AR-15 in the Waffle House parking lot and then stormed the restaurant, police say. Four people were killed and four others were injured before a quick-thinking customer wrestled the assault weapon away, preventing more bloodshed.

Metropolitan Nashville Police Chief Steve Anderson said at a news conference that Reinking, 29, was last seen Sunday around a wooded area near an apartment complex where he lived, wearing only pants and no shirt or shoes.

Anderson said it's not clear why Reinking opened fire on restaurant patrons, though he may have "mental issues."

He may still be armed, Anderson said, because he was known to have owned a handgun authorities have not recovered.

"He's on foot," Anderson said. "Unless he's been picked up by a car, he would be fairly close. We don't want to alarm people, but certainly, everybody should take precautions. It could be he's in an unoccupied house. We want everybody to be concerned. Neighbors should check on each other."

Nashville public schools will go into "lock-out" mode if Reinking isn't found in time for class Monday, officials said. That means students will be free to move about the building, but no guests or visitors will be allowed to enter.

As the search continued, authorities in Illinois shared past reports suggesting multiple red flags about a disturbed young man with paranoid delusions.

In May 2016, Reinking told deputies from Tazewell County, Illinois, that music superstar Taylor Swift was stalking him and hacking his phone, and that his family was also involved, according to a report released Sunday.

Another sheriff's report said Reinking barged into a community pool in Tremont, Illinois, last June, and jumped into the water wearing a pink woman's coat over his underwear. Investigators believed he had an AR-15 rifle in his car trunk, but it was never displayed. No charges were filed.

Last July, Reinking was arrested by the U.S. Secret Service after he crossed into a restricted area near the White House and refused to leave, saying he wanted to meet President Donald Trump. Reinking was not armed at the time, but at the FBI's request, state police in Illinois revoked his state firearms card and seized four guns from him, authorities said.

The AR-15 used in the shootings was among the firearms seized.