APS Police Chief Marquenta Sands said that several people witnessed the incident, which took place as students were changing classes.
Metal detectors were working when the shooting occurred, but Tukes navigated around them, Sands said. Tukes arrived late and another student opened a gym door for her to get in.
Sands said that the gun was lying on the ground near the scene until APS school detectives arrived and secured it.
Sands acknowledged that there were rumors that some students knew that Tukes had a gun on campus. She said that Grady High School has started a tip box in the discipline office where students can provide anonymous tips to administrators.
In response to a parent's question, Sands said that police have found no indication that Tukes was associated with any gangs, but they are investigating that possibility. She says students might soon get similar training like staff to spot gang activity and other problems.
"We are looking at exploring opportunities to do the same with our students," Sands said.
The school's principal said that Tukes was "not a troublesome kid."
Sands acknowledged that there are gaps in security and pledged that authorities are working to address them.
Parents said they were concerned about keeping in touch with their children during emergencies. School policy states that students' cell phones should be turned off during school hours.
"It's very important to us that our kids be able to have an access to their cell phones," one parent said.
Many parents told FOX 5 said that the meeting alleviated some of their fears, but said that more needs to be done be done to keep the lives of communication open between the schools, students and parents.
"They do need to be in tuned to what we can do to kind of close some of the gaps and they kind of reassured me that that would happen," said Kate Yeager
School officials said that students will be able to voice their concerns on Friday during their home room periods.