The teen, who has not been identified, was helping investigators Tuesday morning to find the gun, which he said was a 9 mm handgun he "tossed nearby."
The death toll from the Texas rampage rose to seven on Sunday morning. The gunman is also dead.
Trump's visits to Dayton and El Paso were intended to unite and heal, but his words preceded him and he was greeted by large, angry protests.
Researchers have long sought links between real-world violence and bloody video games. "We found a whole lot of nothing," said one expert.
A gunman opened fire at a Walmart Saturday, killing 22.
Nine people were killed in the shooting hours after 20 people were killed by a gunman at an El Paso, Texas, Walmart. Officials in Texas announced Monday another victim had died.
President Donald Trump condemned "bigotry and hatred" following last weekend's mass shootings in El Paso, Texas, and Dayton, Ohio.
Juan de Dios Velazquez had only moved to El Paso, Texas, with his wife Estela Nicolasa from Ciudad Juarez, just across the border in Mexico, six months before they were caught in Saturday's mass shooting at a Walmart store.
All the victims were identified by Ohio officials on Sunday as well as the gunman.
JT Lewis, whose younger brother Jesse was killed in the Sandy Hook Elementary School shooting in 2012, announced Monday he's running for state senate in Connecticut.
In a passionate speech on gun violence, the New Jersey senator stood out from a crowded field of Democratic presidential contenders.
A veteran municipal employee opened fire in Virginia Beach on Friday, killing 12 people on three floors and sending terrified colleagues scrambling for cover.
A worshipper at the California synagogue where a gunman opened fire, killing one woman, has told how he confronted the teenage shooter.
Six people have been shot dead by the security forces in the Somalian capital Mogadishu
"The military has always been a good way to sell firearms," a gun-marketing researcher said.
"It's actual heartache that people have so much hate for who you are. That they hate everyone you know — people who are wonderful people," one Pittsburgh Jewish teen said.
Politicians and world leaders condemned the deadly shootings at two mosques in New Zealand on Friday
A suspected white supremacist has been charged with murder in New Zealand.
Criminal violence in the region centers around the theft of fuel from a nearby oil refinery.
Brazilian police killed at least 13 suspected drug traffickers on Friday in a shootout in Rio de Janeiro.
Witnesses of the shooting near the Christmas market in Strasbourg, France, have spoken to Euronews about what they saw.
The Russian President also linked the rampage, in which at least 20 people were killed, to US school shootings.
Here's our afternoon round-up of the key stories from Europe today.
Witnesses and victims shared their stories as the shooting took place, before talk turned to false speculation on the shooter's identity
Wireless signals can penetrate bags to get the dimensions of dangerous metal objects, including weapons and batteries for bombs, as well as estimate the volume of liquids such as chemicals for explosives.
Shooting happened after Caribbean carnival.