As the suspect in the vicious fatal stabbing of a Palestinian refugee boy in Illinois is expected to appear in court Monday, as FBI Director Christopher Wray expressed concerns that the unprecedented violence erupting in Israel and Gaza will spill over to United States as more domestic "lone actors" seek to spread antisemitic or Islamophobic hate.

Joseph Czuba, the 71-year-old man accused of killing 6-year-old Wadea Al-Fayoume by stabbing him 26 times, and then stabbing his mother repeatedly in their suburban Chicago home on Saturday, is expected to be arraigned on charges of first-degree murder and state hate crimes when he appears Monday afternoon at the Will County, Illinois, Courthouse in Joliet, officials said.

Around the same time, mourners are expected to gather for Wadea's funeral.

"He was a lovely boy who loved his family, his friends. He loved soccer, basketball, and he paid the price for the atmosphere of hate," Ahmed Rehab, president of the Council on American-Islamic Relations in Chicago, said during a news conference Sunday.

The disturbing incident prompted President Joe Biden to issue a statement saying he was "sickened" by the crime.

"This horrific act of hate has no place in America, and stands against our fundamental values: freedom from fear for how we pray, what we believe, and who we are," Biden said.

U.S. Attorney General Merrick Garland has instructed the Chicago FBI Field Office, the Civil Rights Division of the Department of Justice, and the U.S. Attorney's Office for the Northern District of Illinois to open a federal hate crimes investigation into the killing.

"This incident cannot help but further raise the fears of Muslim, Arab, and Palestinian communities in our country with regard to hate-fueled violence," Garland said in a statement. "The Department of Justice is focused on protecting the safety and the civil rights of every person in this country."

The killing happened Saturday morning in the unincorporated community of Plainfield Township, Illinois, when Wadea's 32-year-old mother, Hanaan Shahin, answered a knock on the door of her ground-floor apartment and was confronted by her landlord, Czuba, allegedly yelling hateful comments and wielding a military-style knife, according to Will County Sheriff's Office investigators.

"He knocked on the door and ... he attempted to choke her, and said, 'You Muslims must die,' and attempted to stab her, and stabbed her. And she went to the bathroom and called 911. And this was all in her own words," Rehab said at the news conference, which was attended by the slain child's father, who was too emotionally shattered to speak.

After allegedly stabbing Shahin 12 times, Czuba is accused of unleashing his rage on her little boy, who turned 6 just last month, stabbing him repeatedly, authorities claim.

In a statement Monday, U.S. Secretary of Homeland Security Alejandro Mayorkas also condemned the child's slaying.

"There is no humane world that can and should tolerate the murder of an innocent child because of his identity," Mayorkas said. "The tragic events in the Middle East, begun by the brutal terrorist attacks by Hamas, have brought ideologies of hate to the fore across the world -- notably antisemitism and Islamophobia. This must end. The diversity and inclusiveness that define America must prevail."

During his annual remarks to the International Association of Chiefs of Police on Sunday, FBI Director Christopher Wray echoed the message of vigilance as the Israel-Hamas conflict continues to unfold.

While authorities say there have been no specific credible plots against the U.S. discovered in the wake of the Oct. 7 terrorist attack by Hamas in Israel and the Israeli military response, Wray said there has been an increase in reported threats that U.S. law enforcement is aware of and is investigating.

"In this heightened environment, there's no question we're seeing an increase in reported threats, and we have to be on the lookout, especially for lone actors who may take inspiration from recent events to commit violence of their own," Wray told the chiefs on Sunday. "And I'd encourage you to stay vigilant, because as the first line of defense in protecting our communities, you're often the first to see the signs that someone may be mobilizing to violence."

The New York Chapter of the Council on American-Islamic Relations condemned alleged anti-Palestinian attacks that occurred in Brooklyn last week, and called on public officials and the media to end anti-Palestinian incitement.

The NYPD hate crimes unit confirmed it is investigating several reported anti-Palestinian and antisemitic assaults in New York that have occurred since the Hamas surprise attack on Israel. In one incident that occurred on Wednesday in Brooklyn, police told New York ABC TV station WABC that two Jewish men approached two other men holding Palestinian flags, grabbed one of the flags and hit one of the victims with it before running away.

On Wednesday night, two 16-year-olds allegedly fired gel pellet guns outside congregation B'Nai Yosef in Brooklyn. Police said the teens were taken into custody by the Flushing Shomrim, a Jewish watchdog group. Later that same night, an 18-year-old Middle Eastern man was allegedly assaulted by one of three men waving Israeli flags. Police said the men got out of their cars and asked the victim if he was Palestinian before one allegedly kicked and punched him, according to the NYPD, which is investigating the incident as a possible hate crime.

"Let me be clear: New York has zero tolerance for hate of any kind, not now and not ever," New York Attorney General Letitia James said in a recent statement. "As we mourn the loss of innocent Israeli and Palestinian lives, there is no excuse or tolerance for antisemitism, Islamophobia, or bigotry and discrimination of any kind. No New Yorker should fear walking in our streets because of what they wear, what they believe, or where and how they practice their faith. I encourage anyone who experiences a hate crime or bias incident to report it to my office."

In Fresno, California, police arrested a suspect who vandalized a bakery on Oct. 10 that he mistakenly thought was owned by a Jewish family. The owners, who are Armenian, told ABC affiliate station KFSN that the suspect was captured on surveillance video shattering their front window with a rock and leaving behind a note reading, "All Jewish businesses will be targeted."

Fresno police also said a Jewish temple was vandalized that same day, and that officers are investigating whether the man arrested in the bakery attack is also responsible for the damage done to the synagogue.

ABC News' Jack Date contributed to this report.