The O'Rourke campaign says over 5,000 people attended.
Sporting an Uvalde hat, O'Rourke spoke on a variety of issues including reproductive choice, voter access, and reforming gun laws.
"We're going to win, because we're fighting for every woman to make her own decisions on her body, her own future, her own healthcare. We're going to win, because we prioritize the lives of our kids over the interests of the NRA," O'Rourke said.
"There's just a huge teacher shortage. We can't find teachers, and the kids are the ones who ultimately suffer. We need to have some change in the education system, looking forward to what Beto does in education," attendee Margie Webber said.
"We're excited to have somebody who supports teachers, because we seriously lack teachers, and we need help in the classroom. Abbott has done nothing, nothing since Uvalde, he hasn't done anything to help teachers," another attendee said.
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O'Rourke said he would fully fund law enforcement, as well as training and holding those who abuse their power accountable.
The family of one of the Uvalde victims was in the audience. "We are so lucky right now to be joined by some of the family members of Jackie Cazares," O'Rourke said.
When talking about the 19 students that were killed, he said, "they're absolutely defenseless against a governor who refuses to lift a finger to prioritize their lives. 19 weeks and nothing has been done."
"We don't need to call a special session in order to take action. For six consecutive days after the shooting took place, I issued directives to make schools safer and respond to the emergency in Uvalde," Gov. Greg Abbott said in the gubernatorial debate Friday night.
In the debate, Abbott defended his pro-life stance. After the Supreme Court decision to overturn Roe v. Wade, he said Texas prioritizes supporting women's healthcare so they can choose life for children. Meanwhile, on education, he spoke about the funding he's provided for teachers. On gun laws, he said it's unconstitutional for a state to raise the age to buy an AR-15 to 21.
After O'Rourke's speech, Willie Nelson played a few songs, including "Vote 'Em Out."
"I'm a big Willie fan," Webber said.
Nelson ended his performance by saying, "To you folks there, the parents who've gone through some incredibly sad times, remember that it's not something you get over, but it's something you get through. Thank you."
Early voting will start on Oct. 24. Election Day is Nov. 8.