New York City's deadliest shooting in 25 years – in a state with some of the toughest gun laws in the nation – is raising questions about how a gunman with a history of mental health issues was able to obtain multiple firearms and drive undetected across several states to carry out the attack. The gunman who walked into a Midtown Manhattan office building on Monday, M4 assault-style rifle in hand, and sprayed it with gunfire, hada license to carry a concealed weaponin his home state of Nevada, officials said. He also had been placed on psychiatric hold in 2022 and 2024, law enforcement sources told CNN. But that may not have necessarily prohibited him from obtaining his license in 2022 or buying firearms – depending on the circumstances of the holds, according to gun law experts. Shane Devon Tamura, 27, of Las Vegas, killed four people at the 345 Park Avenue office building and injured anotherbefore he died by suicide,police said. While public health expertscontinue to stressthat the vast majority of people experiencing mental health challenges are not violent, questions remain about the details of Tamura's psychiatric holds and if they would have shown up in a background check. The case underscores the wide gap in sharing mental health data with the federal government – an issue that can be attributed to inadequate funding to manage or require the data, as well as privacy issues, according to Thomas Chittum, former associate deputy director of the Bureau of Alcohol, Tobacco, Firearms and Explosives. Tamura had "a documented mental health history," according to New York Police Department Commissioner Jessica Tisch, and a previous run-in with law enforcement. Tamura was arrested and charged with misdemeanor trespassing in 2023 in Clark County, Nevada, after he refused to leave a Las Vegas casino after attempting to cash out about $5,000, according to a police incident report. A court database suggests a district attorney declined to pursue the case, meaning the incident wouldn't have prevented him from obtaining a gun. The case also throws private gun sales under the microscope. The AR-15 style weapon used in the shooting was legallypurchased last year by the gunman's supervisorat the Vegas casino where he worked, two law enforcement officials told CNN. The supervisor then assembled it and sold it to Tamura for $1,400, the officials said, citing an interview with the supervisor who is cooperating with authorities. It's not yet clear whether the private sale between Tamura and the supervisor involved a background check. But the supervisor, who has not been named by authorities, could face legal jeopardy if the investigation reveals the firearm transfer took place in Nevada and the private sale didn't follow a state law requiring background checks for private sales, according to Warren Eller, gun violence expert and associate professor at John Jay College of Criminal Justice. As police work to uncover a motive behind the shooting, investigators are digging into Tamura's history and examining are how he obtained multiple firearms and made his way from Las Vegas to New York City with the assault rifle. A search of the gunman's car turned up a host of items, including additional ammunition, another loaded weapon, headphones potentially used for target practice, two cell phones, the antidepressant Zoloft and cannabis, a law enforcement source told CNN. A note found in the gunman's pocket claimed hehadCTE, a disease linked to head trauma, one that's often associated with football players, a source told CNN. New York City's chief medical examiner's office will test Tamura's remains for CTE, an office spokesperson told CNN Tuesday. The only way to diagnose the disease is through an autopsy of the brain. As for the psychiatric holds, it's difficult to say without knowing the details whether they would have shown up in a background check or prevented Tamura from purchasing weapons, experts say. "If you were on a 48-hour hold, if you were released at the end of that, it would not affect your ability to possess firearms under federal law," Chittum said. Most states barely touch on the area of mental health when a person applies for a gun license due to concerns over privacy issues and stigmatizing people who have mental health issues, according to Eller. One concern, for example, is soldiers who struggle with post-traumatic stress disorder, or PTSD, might be reluctant to seek help because they fear their treatment history would deprive them of possessing firearms. "Between the lack of funding to make sure the background check system is effective for those problems and the legal hang ups with advocacy groups who will challenge this, that's a long road ahead," Eller said. There's a concerted effort by veterans' groups and advocacy organizations like the American Civil Liberties Union to fight against the sharing of mental health records with the National Crime Information Center and local law enforcement, which most states rely on for background checks, according to Eller. "Groups have been combating that because simply being mentally ill doesn't mean you're mentally incompetent, nor does it mean you're a danger," he added. However, in cases where a person was declared incompetent by a court, faced a restraining order, involuntarily committed or deemed a danger to themselves or others due to a mental illness, the federal government restricts firearm ownership and states largely follow federal law with some variations, according to Chittum. "Even when we have someone who has a mental health issue that prohibits them under the law, the next question is whether the background check identifies that. Historically, mental health records have been some of the hardest for FBI to obtain when doing background checks," Chittum said, adding there have been efforts to improve the availability of those records in some legislation. As New York homicide detectives work to piece together a timeline of events leading up to the deadly Manhattan attack, the way Tamura obtained the high-powered M4 rifle from an associate and whether Nevada's background check laws were violated will likely come under scrutiny. In Nevada,the private sale of a firearm between two partiesrequires a federal background check before the transfer is complete. Both individuals must go to a federally licensed firearm dealer, which conducts the background check on their behalf. There are limited exceptions, including firearm transfers between immediate family members, which do not require this process. If the private sale between Tamura and the supervisor did abide by the law and the facts can't prove the supervisor had any knowledge of possible disqualifiers in Tamura's history, including intended use of the firearm, then the seller likely won't be prosecuted, according to Eller and Chittum. Federal law doesn't impose any obligation on private gun sellers to identify the buyer, conduct a background check or keep any record of the sale, Chittum said. The Nevada law enforcing background checks for private sales was implemented in January 2020, closing the so-called "gun show loophole" that gun safety advocates have long criticized as a means for bypassing records checks that can flag past criminal history. Most states conduct background checks through federally licensed dealers relying on the FBI's National Instant Criminal Background Check System (NICS), while some states like Nevada have a designated "point of contact" system that offers access to state criminal history records. Under federal law, an unlicensed person buying a firearm directly from a gun dealer must also undergo a background check, however, those who already have a concealed carry permit – like Tamura had – may be exempt because they would have already undergone a background check to get the permit. Hours after the shooting in Manhattan, Las Vegas Police Crimestoppers received a tip from a licensed firearms dealer saying he remembered Tamura sought to buy anaftermarket trigger assemblyfor an M4 rifle at a Las Vegas gun show in June, a senior law enforcement official told CNN. Tamura returned the trigger assembly the next day, saying he needed the money back to buy 500 rounds of .223 ammunition – the same kind of ammunition used in the New York shooting, according to the official. The gun dealer told police Tamura came back the next day with additional funds and re-purchased the trigger assembly, the official said. Tamura's case calls attention to the "gray area" in the federal regulation and enforcement of private sales that exists when people buy firearms for cash in a private sale, according to Eller. Because a concealed carry permit would exempt an individual for five years from a background check when buying a firearm from a licensed dealer, it creates a "nuanced area" where a person could obtain a license to carry and then subsequently be convicted or have a mental health prohibitor and might still be able to use their card to purchase a firearm and avoid the background check, Chittum said. Some states recognize this issue and routinely run background checks on licensed holders to determine if their license is still valid, Chittum said. Red flag laws, including the one in Nevada, aim to keep guns out of the hands of those who pose a threat to themselves or others. But such laws are only effective if the individual demonstrated warning signs so that others can alert law enforcement and initiate the process of revoking the person's firearm, Chittum said. It's not clear if Tamura demonstrated any warning signs that would trigger the state's red flag law. The style of weapon Tamura used to slaughter four peoplehas commonly been seenin some of the nation's deadliest mass shootings and has prompted renewed calls by progressive lawmakers for increased regulation. "In the State of New York, you cannot buy one of these," Gov. Kathy Hochul told CNN on Tuesday, criticizing what she said were "much looser laws in the State of Nevada than we have here." Hochul called on federal lawmakers to pass a national assault weapon ban that would limit access to high-powered guns like the AR-15 style rifle used in Monday's massacre and slammed GOP counterparts whom she accused of being "intimidated by the gun lobby." "We need a national awakening here, people need to be talked about this once again and it shouldn't just happen in the wake of a tragedy like this," said Hochul. CNN's Mark Morales contributed to this report. For more CNN news and newsletters create an account atCNN.com
