'Daddy, help! They're killing me!'

Editor's note: Ruben Navarrette Jr. is a CNN.com contributor and a nationally syndicated columnist.

San Diego, California (CNN) -- As evidenced by media stories and public awareness campaigns, Americans have resolved to get tough on bullying. In that spirit, it's time to send a message to bullies with badges.

We need to tell police who prey on the vulnerable: "No more! When you pile on a suspect and beat him to death, we will treat you just like any other alleged criminal. We will arrest you and prosecute you. And if convicted, you will go to prison for a very long time. We will make an example out of you so that other police officers will think twice before abusing their power."

The messenger could be the jury that will hear the case against two police officers in Fullerton, California, a city about 25 miles southeast of Los Angeles. A judge ruled Wednesday that the officers will stand trial in the beating death last July of Kelly Thomas, a 37-year-old homeless man afflicted with schizophrenia.

Cpl. Jay Patrick Cicinelli is charged with involuntary manslaughter and felony use of excessive force. Officer Manuel Ramos faces the more serious charge of second-degree murder, because prosecutors believe he took a more active role in the assault. Both officers have pleaded not guilty.

Ruben Navarrette Jr.

This week, at the preliminary hearing to determine whether enough evidence supports proceeding with a trial, prosecutors aired a graphic video of the savage beating. The footage shows about a half dozen officers punching and kicking and putting pressure on Thomas' chest, firing electric shocks from a Taser stun gun, all to supposedly subdue a suspect well beyond the point where he is resisting or capable of resisting arrest.

Early on, Ramos appears to tell the young man who is sitting on the ground: "You see my fists? They're getting ready to f--- you up!" Another police officer is heard saying: "We ran out of options so I got to the end of my Taser and I ... smashed his face to hell."

By the end of the video, Thomas is lying in a pool of blood. According to prosecutors, the young man suffered brain injuries, facial fractures, broken ribs and extensive bruises and abrasions. He died five days later.

What we see in that 33 minutes of footage, including a defenseless Thomas screaming in pain, saying he's sorry and pleading for help, should never happen in the United States of America. When it does happen, it can't be tolerated, justified, or excused.

That's coming from the son of a retired cop. My father wore a badge for 36 years, and he has no stomach for police brutality. In fact, about 20 years ago, when another piece of videotape surfaced -- that of the Rodney King beating by police officers in 1991 -- I remember my father telling me that, as far as he was concerned, those out-of-control law enforcement officers wailing on King had ceased being cops and become little more than thugs and criminals.

Video shows cops beating homeless man

As it turns out, Thomas' father is also a retired law enforcement officer. After his son died, Ron Thomas made it his mission to make sure the story got out and would not be forgotten. He used social media and the Internet to show the world what those officers had done to his son, complete with graphic photos that he took at the side of Kelly Thomas' hospital bed.

This is a good dad. But he was also, apparently, a good cop who trained fellow deputies on the right way to take down suspects. This is the wrong way. Thomas described the officers' actions as nothing less than a "hate crime against the homeless and mentally ill."

Last year, Fullerton city officials offered Thomas nearly a million dollars to settle the case. He turned it down, and instead pushed for a criminal trial.

This should bring some small comfort to Ron Thomas. He needs it. He has to carry around with him for the rest of his life that, as his son was fighting for his life, he cried out for his father to protect him from these bullies. On the video, we hear Kelly Thomas screaming: "Daddy, help! They're killing me!" As a father myself, those words break my heart.

"Daddy, help! They're killing me!"

He was killed. And now, if the cops are convicted of this crime, they have to pay.

The opinions expressed in this commentary are solely those of Ruben Navarrette Jr.