Although the event was held on school grounds, the event was not for Mount Zion High School students, but was a a commencement for graduates of the Perry Learning Center, an alternative high school that prepares students for careers, reported Fox 5 Atlanta.
It was only when he reached the exchange program that he got the bad news: Sabika Khan was among the 10 people killed in Friday's mass shooting at Santa Fe High School, southeast of Houston.
After the ceremony an argument broke out in a parking lot outside the venue, police said.
Pagourtzis has been charged with capital murder and aggravated assault of a police officer.
Another 10 people were wounded. During the appearance, the teen acknowledged understanding the charges against him, only saying "yes, sir" and "no, sir" when asked questions.
Police: 1 dead, 1 hurt in shooting after Georgia graduation
Crime scene tape is stretched across the front of Santa Fe High School on May 19, 2018 in Santa Fe, Texas. At a vigil for the victims in the center of Santa Fe on Friday night, Ray told NPR's John Burnett that he would have never suspected his former teammate was capable of mass murder - he was just joking with the suspect on a field trip to a Galveston water park on Thursday, the day before the massacre.
Gubernatorial candidate Andrew White, one of two Democrats vying for the post, urged Republican Gov. Greg Abbott to "open his mind to protect our kids" by calling a special legislative session to change gun laws and spend money to harden Texas schools.
Authorities later found explosive devices - including pipe bombs and pressure cookers - in and near the school, a law enforcement official said.
Henry told reporters that the suspect had devices but none were functional. Authorities had earlier said that nine students and one teacher were killed.
"You can do this with anything", said Pearson, who sometimes drove the alleged shooter, Dimitrios Pagourtzis, home from practice. Michael Farina, 17, said he was on the other side of campus when the shooting began and thought it was a fire drill. But authorities now believe those two were not connected to the crime, the official said.More news: IPL 2018: RCB survive Williamson scare to stay alive
Santa Fe High School, southeast of Houston, became the scene of the fourth-deadliest mass shooting at a US public school in modern history, joining a long list of campuses where students and faculty have fallen victim to gunfire.
Thirteen people suffered injuries from the gunfire, including school district police officer John Barnes, who was taken to the hospital in critical condition.
"While we remain mostly in the dark about the specifics of (Friday's) tragedy, what we have learned from media reports seems incompatible with the boy we love", the family said.
This is the 22nd United States school shooting so far this year, and the third instance in eight days in which a gunman was on a school campus. "I am so sorry this epidemic touched your town - Parkland will stand with you now and forever", Marjory Stoneman Douglas student Jaclyn Corin said in a tweet.
"We will once again laugh", he said.More news: Distant galaxy hints at universe's earliest stars
"It's been happening everywhere", she said.
Freshman student Abel San Miguel told the AP that Chris Stone was one of the students who tried to block the door to an art classroom to prevent the shooter from entering.
"A week later he opens fire on everyone he didn't like", she said. "And then everybody starts running, but, like, the teachers are telling us to stay put, but we're all just running away".
"I didn't see anybody shooting, but, like, (the gunshots) were kind of spaced", Angelica said, adding she heard about four shots.
"He wore, like, a trench coat nearly every day", student Mateo Twilley told CNN.More news: Next CW superhero crossover to introduce Batwoman
Acevedo said he was "not ashamed to admit I've shed tears of sadness, pain and anger" after the shooting.