ATLANTA (AP) — Many questions in last week’s Georgia school shooting are still unanswered, including how the suspect brought a semiautomatic assault rifle to the campus of Apalachee High School and what may have motivated the violence.

The shooting Wednesday in Winder, northeast of Atlanta, killed two teachers and two students. Another teacher and eight more students were wounded, with seven of those hit by gunfire.

Colt Gray, 14, is charged as an adult with four counts of murder, and District Attorney Brad Smith has said more charges are likely to be filed against him in connection with the wounded. Authorities have also charged his father, Colin Gray, alleging that he gave his son access to the gun when he knew or should have known that the teen was a danger to himself and others.

In the meantime, relatives are mourning the victims, including teachers Richard Aspinwall, 39, and Cristina Irimie, 53, and students Mason Schermerhorn and Christian Angulo, both 14.

The 13,000 students at Barrow County’s other schools are supposed to return to class Tuesday. Officials have not announced a restart date for the 1,900 students who attend Apalachee.

Superintendent Dallas LeDuff, in a video message Sunday, said sheriff’s deputies and state troopers will provide extra security when schools reopen Tuesday, with extra counseling available at all campuses.

Here’s a timeline of what happened on the day of the attack, based on statements by authorities and reporting by The Associated Press and other news media:

8:15 a.m. — First period begins. Officials have not said what class Colt Gray was scheduled for, or if he attended. It’s also unclear how Gray got to school that morning or if he was carrying the rifle with him.

9:38 a.m. — First period ends. Students have seven minutes to change to their next class.

9:45 a.m. — Second period begins. Student Lyela Sayarath said she briefly saw Gray in the algebra class where the two sat next to each other. But Gray left the room. Sayarath said she assumed Gray was skipping class, but it’s not clear where he may have gone.

9:50 a.m. — Marcee Gray, Colt’s mother, calls the high school from 200 miles away in Fitzgerald, Georgia, to warn that her son is having an “extreme emergency,” according to call logs, texts and an interview by Gray’s aunt, Annie Brown, with The Washington Post. Brown later confirmed the account to the AP but declined to comment further.

Brown said the mother texted her saying she spoke with a school counselor and urged them to “immediately” find her son to check on him. Call logs show the call lasted until 10 a.m. Relatives of Marcee Gray have told multiple media outlets that she received a text from her son that morning saying he was sorry, without saying what he was apologizing for.

9:45 a.m. to 10:20 a.m. — An administrator comes to the algebra classroom looking for a student with the same last name and a similar first name to Colt Gray, Sayarath said. The other student is in the bathroom, she said, but the administrator takes the other student’s bag. When the other student returns, he tells Sayarath that the administrator was actually seeking Colt Gray. In the meantime, the teacher is called on the intercom, Sayarath said.

About 10:20 a.m. — Colt Gray approaches the door of the algebra classroom. As the intercom buzzes again, the teacher responds, “Oh, he’s here,” seeing Gray outside the classroom door, Sayarath said. When students go to open the door, which automatically locks from the inside when closed, Sayarath said they backed away. She said she saw Colt Gray turn away through the window of the door and then she said she heard 10 or 15 consecutive gunshots. People are shot in the hallway and inside at least one classroom, as others in the halls scramble for safety. According to some students, the three teachers are shot while trying to shield students.

10:23 a.m. — After multiple employees press wireless panic buttons embedded in their employee badges, the school goes into lockdown and a massive law enforcement response begins. Students in other classrooms who hear the gunshots begin texting and calling their parents and others.

10:26 a.m. — The two school resource officers assigned to Apalachee High School approach Gray in the hall, according to GBI Director Chris Hosey. Gray immediately surrenders and is taken into custody.

About 11 a.m. — Law enforcement officers begin searching Colin and Colt Gray’s house east of Winder. At the school, officers go from classroom to classroom, first looking for more people with injuries or other shooters. Later, officers evacuate students to the football field as hundreds of parents rush to campus.

About 1 p.m. — The school begins releasing students to parents to take them home.