A report published by the APA says that fewer than 1 percent of firearm homicides are committed by a person diagnosed with a mental illness.
"If all our government and president can do is send 'thoughts and prayers,' then it's time for victims to be the change," said one student.
"There's no disrespect or insensitivity intended by this long-planned gun show," a statement from organizers said.
It was the strongest recorded earthquake in the area for more than 100 years, according to the British Geological Survey.
Thirteen people were killed and 15 hurt in Oaxaca after a military helicopter carrying Mexico's interior secretary and a state governor crashed.