The support rally was held at the corner of Nordhoff Street and Sepulveda Boulevard less than a mile from the murder scene.
Prosecutors say Shehada Khalil Issa, 69, shot and killed his son, Amir, outside their North Hills home last week for being gay.
Los Angeles police officers arrested Issa after finding Amir's body outside the home. The Los Angeles County District Attorney's Office said Friday that Issa had previously threatened to kill his 29-year-old son because of his sexual orientation.
The suspect told police he shot his son in self-defense after he discovered his wife's body in their home. Rabihah Issa, 68, was found stabbed to death but an investigation into her murder is ongoing.
Organizers say they held the rally to advocate for family acceptance toward all LGBTQ children as well as to demand an end to discrimination and violence.
"When one of these family tragedies happen, this sends a strong message that there's a lot more work that we need to do, anti-violence work, work to educate our communities to rise above homophobia and transphobia and most importantly, to really address mental health issues," rally organizer Ronnie Veliz said.
Issa is being held without bail on one count of premeditated murder as a hate crime. He's scheduled to be arraigned at L.A. County Superior Court on April 11. If convicted as charged, he faces life in prison without the possibility of parole.
The Associated Press contributed to this report