Nashville public schools are going into “lock-out” mode today as authorities intensify the search for a gunman who police said opened fire in a Waffle House restaurant early yesterday, killing four before a customer wrestled the weapon away.

Travis Reinking, 29, who was naked during the shooting except for a green jacket and assault rifle, may have “mental issues,” authorities said. He owns a handgun that authorities have not recovered, Steve Anderson, the Nashville Police chief, said.

Police believe that he got home and grabbed a pair of pants.

He was last seen yesterday around a wooded area near an apartment complex where he lived.