The worst mass shooting in U.S. history – at a gay bar in Orlando, Fla. – brings to mind another slaughter of innocents by a madman claiming allegiance to an ideology: the 1977 killing of 77 people, most of them children at a holiday resort, by Norwegian Anders Behring Breivik.

Like Omar Mateen, who paused during his killing spree at the Pulse nightclub to call the emergency number 911 and assert his allegiance to the Islamic State (ISIS), Breivik cloaked his crime in ideology. In Breivik’s case, he was an avid consumer of neo-Nazi and Christian supremacist propaganda. He chose a Norwegian Labor Party youth camp as the main site for his horrific crime to protest that party’s liberal attitude toward Muslim immigration.

So far, there is no evidence that Mateen, who was shot and killed by police, had any concrete links with ISIS or any other organized extremist group. Like Breivik, who was captured and is serving what will likely be a life sentence in prison, Mateen appears to have been a lone wolf.

Unlike several of the perpetrators of another massacre, the November, 2015 shootings of 130 people at multiple sites in Paris, Mateen, 29, had never traveled to Iraq or Syria. Incredibly, however, he was able to purchase weapons legally despite having been twice investigated by the FBI for remarks that suggested sympathy for extremist Muslim groups.

The son of Afghan immigrants, Mateen fits the profile of maladjusted male loners who take revenge on society for their own failings and mental problems. His first marriage broke up because of his abusive behavior, according to his former wife, and co-workers at a security service said he had talked about killing people. Homophobia also appears to have played a role, given his choice of target, a club popular with the LBGT community in Orlando.

ISIS, which is known to murder homosexuals by throwing them off the roofs of tall buildings, was quick to take credit for the horror in Orlando, where 50 people died, but only after Mateen himself asserted the connection. In this, Mateen resembles the couple responsible for yet another mass shooting, last December in San Bernardino, Calif., where 14 people were killed at a Christmas party at a local government center where the male shooter worked.

That incident quickly became fodder for U.S. presidential politics and is believed to have helped Donald Trump win the Republican nomination. It was after San Bernardino that Trump called for a temporary ban on all Muslim immigration to the United States.

In the aftermath of this weekend’s tragedy, Trump repeated that call in a tweet that warned ominously, “Orlando was just the beginning.”

Trump also congratulated himself for being “right” about the immigration ban even though both Mateen and Syed Rizwan Farook, the main San Bernardino shooter, were born in the United States.

In addition, Trump called for President Barack Obama to resign because Obama decried the shooting as terrorism but not “Islamic” terrorism.

It will be interesting to see how well Trump’s Islamophobia plays in the general election campaign that has already started given his status – and that of Hillary Clinton – as their party’s presumptive nominees.

The Orlando massacre follows a week in which Trump has taken a beating from members of his own party for racist comments declaring a judge of Mexican heritage unfit to preside in a suit against Trump regarding his failed “university.” Trump later said his comments had been “misconstrued” but continued to insist that the judge was biased against him. And Trump has not retracted his threat to deport 11 million undocumented aliens, most of Latin American heritage.

Among the many characteristics a president should possess is the ability to act as consoler-in-chief when tragedy strikes. President George W. Bush showed that capacity after 9-11 and Obama has also done so repeatedly after natural disasters and dozens of mass shootings.

On Sunday, he again performed this service urging Americans to “draw inspiration from heroic and selfless acts — friends who helped friends, took care of each other and saved lives. In the face of hate and violence, we will love one another,” Obama said. “We will not give in to fear or turn against each other. Instead, we will stand united, as Americans, to protect our people, and defend our nation, and to take action against those who threaten us.”

It is hard to imagine Trump giving such remarks.