Travis Reinking exhibited multiple warning signs that he was mentally unstable: He talked openly about delusions that he was being stalked by Taylor Swift. He insisted unknown people were making barking noises outside his home. He even went to the White House on a mission to talk to the president. Reinking's behavior resulted in the revocation of his Illinois firearms license, and his weapons were turned over to his father. But authorities say his father simply returned the three rifles and a handgun to his son when he decided to move out of state. The son now stands accused of opening fire Sunday at a Waffle House in Tennessee using an AR-15 that had been among the firearms seized. Four people were killed in the attack. The case illustrates the difficulty of keeping guns away from mentally disturbed people and shows how easy it is for them to retrieve confiscated weapons. 'It's a story of a highly effective law that then has a really dangerous loophole,' said Jonas Oransky, deputy legal director for Everytown for Gun Safety, which works to tighten gun laws. Reinking was disarmed by a man at the restaurant and fled. He was captured Monday. Under federal law, a gun owner's weapons can be seized if that person is convicted of a felony or involuntarily committed for mental health treatment. Illinois is one of the few states with a mechanism to allow firearms to be seized if someone's behavior constitutes a 'clear and present danger' but does not necessarily rise to the level of a felony conviction or an involuntary commitment. Police reports describe Reinking as unstable but not violent. He was well known by local law enforcement, and his troubles were not a mystery to his relatives, who told authorities that he had been having delusions since 2014. In May 2016, Reinking told deputies from Tazewell County, Illinois, that Swift was stalking him and hacking his phone, and that his family was also involved. He agreed to go to a hospital for an evaluation after repeatedly resisting the request, a sheriff's report said. 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 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. 'It seems like they were proactive and effective at suspending this dangerous person's access to guns in the first place, particularly since that's not something they could've done in most states,' said Ari Freilich, a staff attorney at the Giffords Law Center to Prevent Gun Violence. But they 'did not foresee the father being so irresponsible and dangerous in returning the guns to this person.' The father could face charges for returning the guns, according to Marcus Watson, an agent for the Bureau of Alcohol, Tobacco, Firearms and Explosives who spoke Monday at a news conference. Reinking told police last August that he wanted to file a report about 20 to 30 people tapping into his computer and phone and people 'barking like dogs' outside his residence, according to a report. 'There's certainly evidence that there's some sort of mental health issues involved,' Tazewell County Sheriff Robert Huston said Sunday. The sheriff said his department never took formal custody of Reinking's guns. But Reinking's father, who has an Illinois firearm owner's card, was allowed to take them and agreed to 'keep the weapons secure and out of the possession of Travis.' Jeffrey Reinking 'has now acknowledged giving them back' to his son, Nashville police spokesman Don Aaron said. Phone calls to a number listed for the father went unanswered. It is not clear why Reinking moved away from Morton, Illinois, or if he lived elsewhere before settling in Nashville. It's also unclear if the move had anything to do with being near Swift, who has a home in Nashville. Police say he was employed in construction for a while, and there would have been enough work in the booming city for him. Several states have so-called red flag laws that allow relatives, friends or others to go to a court expressing concern about someone being a danger to themselves or others and seeking a court-ordered emergency hearing to consider seizing firearms. But the laws are still rare. After the Parkland shooting, Florida and Vermont — both traditionally gun-friendly states — enacted laws to allow firearms to be confiscated before someone commits an act of violence. States vary in what they do with firearms that are seized. Some states give the option of selling or transferring the guns to a licensed dealer or law enforcement. Others allow the person to give them to a friend, relative or some other third party. Experts caution about the danger of allowing relatives or friends to take possession of the firearms. 'Family dynamics are unusual. And here's a situation where the family knew of his danger and still gave him a gun,' said Adam Winkler, a professor at the University of California Los Angeles School of Law and gun industry expert. Reinking's move to Tennessee — which has considerably more lax gun laws than Illinois — exposes another loophole with the laws, experts say. 'That safety net in Illinois that works so well ... evaporated when he moved to Tennessee,' said Everytown's Oransky. ___ Associated Press Writer Ed White in Detroit contributed to this report.