Sultanbeyli'de silahlı ve sopalı kavga: 2 yaralı  

""Weapons integrated in school, including arms, have already destroyed the ability to have open minds," she said. "Handguns in schools, my God." No guns are allowed inside the school. 
https://www.theguardian.com/australia-news/2017/aug/18/most-australians-oppose-idea-of-armed-teachers-but-vary-with-age-poll 2017 a proposal that all school teachers were
forced to have guns. Students at a Michigan high school in 
Canton teenager were allowed to carry guns in school in 2004. they tried to bring weapons, including a handgun, knife, brass knuckles and 51 rounds of ammunition,into school despite a weapons ban, Sheriff Robert Wright said in a statement issued Monday night. Police also found Air Soft rifles hidden in two backpacks in the car in which the teens arrived. Five students went into the jail with their parents and two students whose parents were not available to take them were released to the custody of juvenile agents.
in 23 US states students are allowed to carry guns in school. in Tennessee, South Dakota, Wisconsin, Oklahoma or Georgia school district students are allowed to use their guns on campus while school is in session.
 Restrictions on weapon possession
Gun tracing is required of licensed gun dealers in the U.S., by federal law. The ATF requires that the gun dealers provide the agency with a record of the sale, manufacturer and; serial number of the gun. All guns have a serial number to be able to trace them. Serial numbers vary between gun manufacturers, but a gun can be traced back from the producer to the first buyer. 
For example, if a gun is used in a crime, a police officer with a gun expert is at the crime scene within hours. The experts look at the burned out casings from the guns and compare them with guns seized from suspects or from off the streets.
The experts can go through this database at the ATF to see if there are similar looking casings or if they are from the same gun. The results in a positive match is give to the police and prosecution. A trace back of the dealer and distributor is then done to find out how the person got the gun.
Code of welcoming refugees
In 2015, a husband and wife murdered 14 people in San Bernadino in the US state of California. At first the husband and wife said they were inspired by ISIS. Later they changed their mind and denied their terrorist involvement. A new bill in congress in 2016 denied U.S. entry for foreigners who intend to commit terrorist acts and for anybody who had been a member of a terrorist organization.
This does not solve the problem that the United States, just as every country, can become a target of terrorism again in the future.