(NewsNation) —  A new federal lawsuit targeting Oxford High School is saying school officials did not do enough to prevent a deadly shooting there last year.

Six families are now suing after four students were killed and seven others were injured in the shooting authorities say was by then-15-year-old Ethan Crumbley.

Investigators say Crumbley returned to class after being in a counselor’s office for a disciplinary meeting with his parents prior to the shooting. The new lawsuit says that was part of the problem and one of the many warning signs that the six families say was ignored and protocol not followed with a student they call suicidal.

The lawsuit claims school officials failed their students.

It’s been an emotional week for Justin Shilling’s family. He was one of the four students gunned down nearly six months ago. He and Madison Baldwin were seniors expected to graduate last week.

“Two of our four students who are taken from us this year happened to be pretty outstanding seniors, and they would have been present with us this evening and graduating with their classmates. We would like to take some time this evening to honor those two students and give them the special recognition they deserve,” a school official announced at the graduation ceremony.

Justin and Madison didn’t walk the stage to get their diplomas; instead, their parents accepted for them. Justin’s parents haven’t talked publicly about the shooting until now. They’ve been grieving, trying to cope day by day.

“It’s been 174 days since he was murdered. And it feels like it was just last week,” the family said.

Justin’s family wanted to get through graduation before this next step.

“We’re beyond heartbroken. We’re traumatized. We’re devastated, and we are not OK,” said Justin’s mother, Jill Soave. “Everything is so hard for us right now. It’s like pushing through mud.”

This new lawsuit alleges warning signs were ignored, suggesting that employees ignored protocol for students experiencing suicidal ideation. It claims that staff had been trained on how to deal with the issue, and that Crumbley met the standards.

“They violated their own policy by sending a suicidal kid back to class without making sure that he didn’t have any dangerous … weapons near him, which would include his backpack that the associate dean of students handed him without looking at that. Obviously, according to the police, they believe that the gun was already in it with the ammunition,” attorney Ven Johnson said.

The school district has not commented on the latest lawsuit. It was not lost on many that while other families gathered to hold graduation parties, the Shilling family filed a federal lawsuit for answers to their son’s death.

“He impacted so many people in 17 short years and never bragged about it, worked tirelessly. His grades were outstanding. You know he was almost too good for this world,” Soave said.

Johnson hopes with this lawsuit, he can get governmental immunity changed. Michigan is one of many states that stops anyone from suing the public school or its employees. He believes this case could end up going to the Michigan Supreme Court and could actually change that law.