"He seemed like a nice kid", she said, although she believed he did not have many friends.
In addition to the nine students and one teacher killed, gunfire wounded ten people, with two of them in critical condition.
The incident came only hours after a gunman killed 10 people and wounded 10 more at a high school in Santa Fe, Texas.
However, Mr Henry, the county's chief administrator, said the canisters had no detonation device and the pressure cooker had no explosive material.
Pagourtzis, who is thought to have no prior arrests or confrontations with law enforcement, made his first court appearance by video link from Galveston County jail on murder charges Friday. The family said the following in a statement: We are saddened and dismayed by yesterday's events at Santa Fe High School.
The New York Times cited an affidavit written by one investigator as saying the suspect had confessed and said he spared "students he did like so he could have his story told".
Yesterday, they said he wore a trench coat to school in Santa Fe, 50km southeast of Houston, on a day when temperatures topped 32C.
The Texas shooting again stoked the nation's long-running debate over gun ownership, three months after a student-led gun control movement emerged from a mass shooting in Parkland, Florida, which left 17 teens and teachers dead.
Officers escorted students and staff back onto school property Saturday, but only to collect valuables.
The shooting unfolded in Santa Fe, a city of about 13,000 people roughly 30 miles (48 kilometers) southeast of Houston. It was also the deadliest assault in Texas since a man with a semi-automatic rifle attacked a rural church late a year ago, killing more than two dozen people.
He and another officer had "engaged" the shooter, Braun said. Braun and other officials declined to answer questions about the investigation.
The Pakistan Embassy in Washington D.C. identified one of the victims on Twitter as Sabika Sheikh, a Pakistani exchange student, while the brother-in-law of Cynthia Tisdale, a teacher's aide and mother of four, said on Facebook she was killed in the attack.
Mourners gather during a prayer vigil following a shooting at Santa Fe High School in Santa Fe, Texas, May 18, 2018.
A third woman, who is pregnant, was pushed to the ground in the chaos after the shooting and taken to hospital, WFAA reported.
Two were listed in critical condition on Saturday at the University of Texas Medical Branch, the hospital tweeted.
Pagourtzis played on the junior varsity football team and was a member of a dance squad with a local Greek Orthodox church.
Rodriguez described her daughter as "shy and sweet" with a passion for video games.
The gunman apparently carried out the attack with a shotgun and a.38 revolver that were legally owned by his father, according to Governor Greg Abbott. It was not clear whether the father knew his son had taken them.