U.S. Rep. Joaquin Castro, D-San Antonio, said Wednesday that he was not doxxing Trump supporters when he tweeted a list of the president's top donors from San Antonio   condemning them for fueling the sort of messaging about an immigrant "invasion" that may have contributed to the massacre in El Paso Saturday.

“Doxxing is when you tell somebody somebody’s physical address or phone number," Castro said in an appearance on MSNBC's "Morning Joe" Wednesday. "None of that was in the graphic here, which was first put up and circulated by an Indivisible group here."

Indivisible is a group, with local chapters across the country, created in the aftermath of Trump's election as an expression of grassroots political opposition.

Castro said he did not want to see those people named on the list harassed. Most were identified from public Federal Election Commission records by their business or line of work, but some of were identified as retirees, or, in one case a homemaker.

"My post was actually a lament,” Castro said. “If you look at my language, I said that it's sad that these folks, many of whom were prominent business owners in San Antonio, a city that's about 65% Hispanic, their customers, the people that have made them wealthy, their employees or people that have worked for them for years, many of those folks are Hispanic, and they're giving their money to a guy who’s running ads talking about Hispanics invading this country."

"So it was a lament about all of us go to the restaurants that these people, the businesses that they own, we patronize these places, and they're giving this money, their money, to this guy who was taking their money and using it to buy Facebook ads, talking about how Hispanics are invading this country," Castro said. "And that there is a cost to that. We saw the cost to that in El Paso over the weekend, that people died. The manifesto that that guy wrote could have been written by the people that write Trump's speeches."

The21-year-old suspect who appears to have driven from suburban Dallas to El Paso, to execute his plan, indicated in an on-line statement linked to him that “this attack is a response to the Hispanic invasion of Texas.”

On Monday night, Castro tweeted a list of 44 San Antonians who had donated the maximum to Trump’s re-election campaign.

“Sad to see so many San Antonians as 2019 maximum donors to Donald Trump — the owner of @BillMillerBarBZ, owner of the @HistoricPearl, realtor Phyllis Browning, etc. Their contributions are fueling a campaign of hate that labels Hispanic immigrants as invaders," the tweet read.

U.S. Sen. John Cornyn, R-Texas, who is up for re-election in 2020, responded with a tweet: "This is grossly inappropriate, especially in the wake of recent tragic shootings. This win-at-all-costs mentality, publicly targeting an opponent’s supporters, and encouraging retaliation is dangerous and not what Texans have a right to expect from their members of Congress."

House Majority Leader Kevin McCarthy tweeted that, “Targeting and harassing Americans because of their political beliefs is shameful and dangerous. What happened to `when they go low, we go high?' Or does that no longer matter when your brother is polling at 1%? Americans deserve better."

On Fox & Friends Wednesday Donald Trump Jr. went a step further.

“That sort of list sort of screams like the Dayton, Ohio, shooter’s list," Trump said referring to the perpetrator of a mass killing that followed the tragedy in El Paso by a matter of hours.

"When a radical left-wing politician, who is polling at about zero percent, does this for either attention or a call to action, it's pretty scary," Trump said. "When the fringe crazies on both sides, and we saw that in the last week, right, you have fringe crazies on all sides, they see it, now you’re going after ordinary citizens who are just participating in the political process. Imagine I did that, imagine I put out a list of Joaquin Castro’s donors."

With his mention of Castro’s low poll numbers, Trump is confusing Joaquin and his twin brother, Julián, the former mayor of San Antonio who is running for president, Joaquin Castro is chairing his brother’s campaign.

Castro noted that the names and occupations of Trump donors on the list he tweeted was readily available public information.

"When you make a political contribution, especially to a federal candidate, that's a public record," he said. "And so that graphic listed people's names, and many of them are business owners, so they actually own those companies."

"These are prominent donors, many of them public figures, but their money is being taken and used to fuel these hateful ads," he said. "And it has put millions of people in this country in fear. There are people right now that are living in fear. And I don't think the president understands that. I don't think those donors understand it, but they need to understand what their money is going to."