In the middle of the national debate on gun control after the murder of 17 people at a high school in Parkland, Florida, there is one detail that has gone almost unnoticed: the fact that the serial killer had repeatedly made racist, homophobic and anti-Semitic comments on social networks.

Was it a coincidence? Or is it that this latest massacre, and several of the previous ones, were in some way related to an increase in racism in the United States?

Nikolas Cruz, the 19-year-old murderer who massacred Parkland students and teachers, had told an Instagram group "I hate Jews, ni**ers, immigrants," according to CNN.

He also wrote there that he wanted to kill Mexicans, keep African Americans chained, and shoot homosexuals "in the … head," among many other racist memes and videos.

Like several other recent serial killers, Cruz used an AR-15 semiautomatic rifle that he had purchased legally at age 18, an age at which, paradoxically, he could not legally buy a beer. Like several other domestic terrorists, Cruz was mentally ill with racist ideas.

A new study by the Southern Poverty Law Center says the number of hate groups in the country increased by 4 percent last year. There are 954 organizations that are against Muslims, Jews, African-Americans, gays and immigrants, they say.

The SPLC report says that the vast majority of these groups, more than 600, are white supremacists. The number of neo-Nazi groups grew from 99 to 121 in 2017, while the number of anti-Muslim groups rose from 101 to 114 in the same period.

The SPLC also affirms that racism is growing in part because of President Donald Trump's hate speech.

"President Trump in 2017 reflected what white supremacist groups want to see: a country where racism is sanctioned by the highest office, immigrants are given the boot and Muslims banned," said Heidi Beirich, an SPLC official. " When you consider that only days into 2018, Trump called African countries 'shitholes,’ it's clear he's not changing his tune."

Former Mexican President Vicente Fox suggested in an interview with Bill Maher of HBO that the serial murder in Parkland was "what you get" when "you speak from the White House with this aggressive and violent language, when you discriminate, when you are a racist."

I'm not going to blame Trump's speeches for the Parkland deaths, but Trump could certainly do much more than he is doing to reverse the rise of racism in the United States, which is giving a pretext to some heavily armed, demented people to go out and kill people.

Among other things, Trump could stop demonizing immigrants, like when he said that most undocumented Mexican immigrants are "criminals" and "rapists." That is a flagrant lie, since the rate of crimes committed by undocumented immigrants is much lower than that of U.S. citizens, according to the Migration Policy Center.

Trump could stop making racist comments, like when he said that a U.S.-born Hispanic judge was not fit to judge a case because "he's Mexican," or when he said that "Islam hates us," as if the 1.6 billion Muslims in the world were all anti-American.

And Trump could stop being so tolerant of neo-Nazi groups, like when he blamed "both sides" for the violence in Charlottesville, Virginia, after a white supremacist attacked a group of anti-racist protesters and killed a woman.

And, most importantly, Trump could show leadership and ask for the prohibition of weapons of war, instead of making crazy proposals such as arming part of the 3.5 million teachers in the United States.

No matter what our political position is, the fact is that there is an epidemic of mass murders and an increase in racism in the United States. That is a dangerous cocktail, and Trump should start doing something to avoid it.