The three-day-long gun-debate beef this week between Houston Police Chief Art Acevedo and the National Rifle Association’s Dana Loesch started with a Facebook post.

“I’m not ashamed to admit I’ve shed tears of sadness, pain and anger,” Acevedo wrote on May 18. “I know some have strong feelings about gun rights but I want you to know I’ve hit rock bottom and I am not interested in your views as it pertains to this issue.”

Acevedo has been a police officer for the past 32 years, 11 of them as chief of a major-city police force in Texas, but there had been nothing like the day he hit rock bottom — May 18 — and the three places he went that day that put him there, he told The Washington Post.

To all my Facebook friends. Today I spent the day dealing with another mass shooting of children and a responding police...

Posted by Art Acevedo on Friday, May 18, 2018

The first was Santa Fe High School. He raced down to the campus, about 30 miles southeast of Houston, with his bomb squad and top brass after the calls for help came in, and he arrived to find a scene of desperation, shock and pain. After hours of trying to organize the chaos, he finally welled up when he and others stopped for a prayer, and he began wondering about the victims, “not knowing who had been gunned down yet, thinking, ‘Are they seniors? Were they planning a party for senior night, graduation?’ ”

The second place he went was to the hospital bedside of the critically injured Santa Fe school resource officer John Barnes, a retired Houston officer who was fighting for his life. And the third trip was to a scheduled memorial for the 114 Houston police officers who have died in the line of duty, many of whom were fatally shot.

He cried on the way home, he told The Post.

“I started reflecting on officers that I personally know,” he said, “a California highway patrolman shot dead, another guy killed by a gang member, another officer gunned down in Austin and having to go to his wife’s house and notify her. The names went on and started racing through my head, and I said, you know? It’s Sandy Hook. It’s Columbine. It’s San Ysidro, at the McDonald’s. There are so many people dying from gun violence, and we do so little to try to address it. We can’t even talk about it without demonizing one another, right? I started realizing, it’s time. I’ve hit rock bottom. It’s time. It became very personal for me that day, because I ended up at a place I had never been, and that’s at a school campus.”

Acevedo’s ensuing Facebook post would be featured in headlines across the country. He started doing more and more interviews. And his comments about gun violence and gun control quickly caught the attention of the NRA. Acevedo, who has long been outspoken about his views on gun violence, has called for universal background checks, particularly to cover the “gun-show loophole,” and stiffer penalties for failure to safely secure firearms in the home, among other things.

On May 21, an NRATV segment titled “Exposing Houston Police Chief Art Acevedo”  aired, hosted by Grant Stinchfield and featuring spokeswoman Dana Loesch. Stinchfield kicked off the segment claiming, “Art Acevedo’s solution to gun violence is to hold law-abiding gun owners responsible for crimes they don’t commit.”

The segment centered on comments that Acevedo made on CBS’s “Face the Nation,” in which he highlighted the fact that the accused Santa Fe shooter took his dad’s shotgun and handgun from home to school. “We’ve got to make sure that everyone stores [their guns] in a responsible manner and that there are significant penalties when they fail to do so and people die as a result of that failure,” Acevedo said.

Loesch pounced, focusing less on guns and more on immigration. She cited Acevedo’s opposition to Texas’s law requiring local jails to cooperate with federal immigration officials and allowing street cops to ask people about their immigration status, which Acevedo has said will make undocumented witnesses of crimes fearful of contacting police.

Loesch, characterizing Acevedo’s position as support for illegal immigration, said this made him a hypocrite.

Acevedo “doesn’t believe you have to enter [the country] legally,” she said, “but thinks he has the right to go into every home in Texas and inspect how everybody’s storing their firearms? I don’t think so.”

Looking back on the past few days, Acevedo says now that he should not have responded to these comments with angry tweets.

But that is what he did.

The comments, he said, misrepresented his views and twisted his words.

“Unlike the @NRATV I believe guns belong in the hands of law-abiding Americans of sound mind and will do everything I can to keep it that way and to keep firearms out of the hands of criminals and the mentally unstable. Goodnight,” he said in one tweet — before continuing with several more.

“Blah, blah, blah,” he said in the next tweet, linking to both a quote from Stinchfield that described him as “a Left-Wing Shill in Cop’s Clothing” and a news article about recent arrests of hundreds of alleged gang members the Houston Police Department made with U.S. marshals.

It would only escalate from there.

Loesch said the next day on her show that Acevedo “decided to have an epic Twitter meltdown.”

“I almost missed it because I was going to bed,” she said.

She described Acevedo’s beliefs as a “gun-grabbing philosophy” — to which Acevedo strongly objected, saying he is a Second Amendment supporter who would fight any policy that confiscated law-abiding Americans’ guns. And then Loesch invited him to come on the show.

Acevedo said no. He also threatened that if NRATV continued to misrepresent his views, he would consider taking them to court. He would be watching them, he said — a comment that became the subject of Loesch’s Wednesday show.

“A free people have the right to call to account elected or nominated political figures,” she said on Twitter. “I will continue to exercise my free speech and do so. You can continue to threaten censorship and surveillance.”

In the future, Acevedo told The Post, “I assure you I will not be engaging them,” saying he turned down Loesch’s invitation to come on the show because he doesn’t believe an actual conversation about gun sense could have occurred there.

But he will keep tweeting and talking about his views on guns, he said, everywhere but on NRA’s TV channel.

“I couldn’t live with myself if something were to happen to one of my children and I couldn’t honestly answer the question ‘What have you done, Chief?’ Not just from a crime-fighting perspective, but from a public-policy perspective,” he said. “I want to be able to say that I’ve done everything I can within my power, which means I’ve spoken up. I’ve stood up.

“I’m tired of people saying there’s nothing that can be done.”