Several parents of students killed in a mass shooting at Santa Fe High School outside Houston, Texas are joining together and are suing the parents of the alleged gunman.

According to the lawsuit obtained by Houston Public Media, the group is alleging the parents of Dimitrios Pagourtzis “failed to properly secure their weapons” and negligently entrusted him with those weapons.

Pagourtzis, 17, allegedly used a .38 handgun and a sawed-off shotgun in his attack May 18 that killed 10 and wounded another 13.

In addition to failure to secure the weapons, the lawsuit says Dimitrios’ parents failed to obtain mental health counseling for their son, failed to properly warn the public of their son’s “dangerous propensities.”

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One Santa Fe High School classmate told CNN Dimitrios was “really quiet and he wore like a trench coat almost every day.”

“The families are united and resolute in their desire to hold the shooter’s parents accountable for this tragedy and want every parent of a troubled child to get that troubled child the help he/she needs and to safeguard their guns from that child,” attorney Clint McGuire said, via Click2houston.com.

The Santa Fe victim’s families are seeking more than $1 million in damages for pain, suffering and funeral expenses.

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“Had the murderer not had available to him the weapons for his carnage, his hidden black rage might well have continued to simmer within, but, the life’s blood of his teacher and peers would not have been so horribly, callously and needlessly spilled,” the lawsuit says, according to the Houston Chronicle.

At the time, the Santa Fe High School shooting was the 22nd school shooting in the United States since the beginning of the year and the second in the state of Texas.