Americans awoke Sunday to the devastating news of the worst mass shooting in the nation's history, reportedly carried out by a U.S. citizen motivated by radical Islam.

Authorities identified Omar Mateen as the lone gunman who attacked a crowded nightclub in Orlando, Fla., at about 2 a.m. armed with an assault rifle and a handgun. Mateen killed 49 people and wounded 53 over two horrifying hours before police stormed the club in an armored vehicle and killed him before more innocent people were slaughtered.

The Florida murders followed by just six months the massacre in San Bernardino, Calif., carried out by a husband-and-wife team who had pledged allegiance to the Islamic State before they killed 14 people and wounded more than 20 at a holiday party.

As with the California case, we'll learn much more about Mateen and his beliefs in the days and weeks to come. Details of the initial investigation were still emerging as this editorial was being written, but already early Sunday authorities said they were treating the attack on the gay club in Florida as an act of terrorism and suggesting that Mateen may have been radicalized.

"We do have suggestions [that the] individual may have leanings toward [that] particular ideology," Ronald Hopper, and agent in charge of the FBI's Tampa Division, said at a news conference. "But right now we can't say definitively, so we're still running everything around."

Once again, shocked Americans are left to grieve — and to question what can possibly be done to prevent further attacks by those committed to mayhem against innocents at home and abroad. By now we know there are no easy fixes, and that demonizing all Muslims is both legally and morally wrong as well as strategically shortsighted.

But Americans should unite in condemnation of radical Islam's hate for gay and lesbian people, which may have motivated Mateen to target the Florida club. The Islamic State and those motivated by its evil dictates want to divide and weaken this country. Our response must be a recommitment to homeland security as well as national unity in the face of hate.