When a gunman opened fire near the student union at Florida State University on Thursday, killing two and wounding six, for student Robbie Alhadeff, the tragedy on his Tallahassee campus brought him back to another school shooting.

Alhadeff’s sister, 14-year-old Alyssa, was one of the 17 people killed in the 2018 Parkland high school massacre in South Florida.

Alhadeff told ABC News Live he was really close to Alyssa, who was a freshman on track to play college soccer when she was gunned down on Valentine’s Day.

On Thursday, Alhadeff said he was walking to his apartment when friends started to text him about the gunfire.

“I ran right back into my apartment because I was scared about the whole situation,” he said.

Alhadeff said he took off at least two weeks of school after his sister was killed. In the wake of Thursday’s shooting, he said his friends are “terrified” to return to class.

“A lot of the people I’m friends with are from Parkland and a lot them go to FSU,” he said. “This is the second time it’s happened — and no one I know wants to go back to school.”

“You could end up being killed just going to learn,” he added.

“I thought this would never happen again,” Alhadeff said, “but it continuously keeps happening — and something has to change.”

Manuel Oliver, whose 17-year-old son, Joaquin, was killed in Parkland, told ABC News Live, “I don’t understand how anyone could be surprised” by another school shooting “if we haven’t done anything to stop it.”

“We will continue to fight — these kinds of events empower us to do more, different things, because whatever we’ve been trying is not enough,” said Oliver, who has become an advocate for gun control.

“You don’t want to be me … so you better get involved,” he said. “You better choose better leaders and ask and demand the safety of your kids.”

Fred Guttenberg, whose 14-year-old daughter, Jaime, was killed in Parkland, said some of Jaime’s former classmates were at the FSU student union when the gunfire broke out.

“As a father, all I ever wanted after the Parkland shooting was to help our children be safe,” Guttenberg, who has become a gun reform supporter, wrote on social media. “Sadly, because of the many people who refuse to do the right things about reducing gun violence, I am not surprised by what happened today.”

The suspect in Thursday’s shooting, 20-year-old FSU student Phoenix Ikner, was shot by officers and is expected to survive, authorities said.

A motive is not known.

The six injured victims are all expected to survive, hospital officials said.

Police have not identified the two people killed but said they were not students.

FSU has canceled classes and sporting events through the weekend. A vigil is set for Friday at 5 p.m.