SWAT members maintain a holding position in Dallas on July 9. A New York man has been convicted of placing fake 911 calls to draw SWAT units to celebrities’ homes. (Carlo Allegri/Reuters)

Federal authorities on Monday identified a New York man as part of a computer hacking group that called armed police to the homes of 20 U.S. celebrities and other prominent people in 2013 — including CNN television host Wolf Blitzer, National Rifle Association leader Wayne LaPierre, a federal cybercrime prosecutor in Massachusetts and members of Congress.

In a case unsealed in Washington, Mir Islam, 22, was sentenced to 24 months in prison for his role in a conspiracy that posted stolen personal financial information about at least 50 people online and also placed false 911 calls about armed shooters at individuals’ homes to draw police SWAT teams to their doors, according to court records, statements and media reports.

There was one false bomb threat to the White House, and a report of an active shooter that disrupted the campus of the University of Arizona, where a cheerleader Islam was obsessed with was a student.

Islam’s online hacking group — called UG Nazi, or Underground Nazi — repeatedly posted the address and Social Security number of Michael Bloomberg when he was mayor of New York, and it directed Web attacks in 2012 against the Nasdaq stock exchange, the Central Intelligence Agency, the states of California and Washington, and the District, authorities said.

The fake 911 calls were “all calculated to result in a risk of dangerous threats of violence” to the victims, U.S. District Judge Randolph D. Moss of the District told Islam, who pleaded guilty to three felony counts of conspiracy, making a false threat involving explosives and stalking.

“This is something that will not be tolerated in our legal system,” Moss said.

Defense attorney Matthew J. Peed, acknowledged that Islam’s offenses were serious and “immature, illegal and wrong” but asked for a sentence of time served, saying they were the work “of a 19-year-old man with mental-health issues” who had cooperated with federal investigators in implicating at least two co-conspirators.

Peed said Islam spent 18 hours a day playing games online and viewed hacking as a form of youthful anarchy or libertarian protest against a “security state.” He was not aligned with any Nazi ideology or hate group, Peed said.

“I thought we were going to get more media because everyone hates Nazis,” Islam told the court in a five-hour sentencing hearing. Islam, who has been jailed since September 2013, called himself a changed man who has received psychiatric care, lost 70 pounds, earned a high school diploma and taught other inmates.

“The mistakes I made before, I have to pay for them, I understand that,” Islam said.

Assistant U.S. Attorney Corbin A. Weiss called Islam a skilled practitioner of Web schemes.

Prosecutors said he engaged in “carding,” or stealing and selling credit card information; “doxing,” or stealing other personal and financial information, such as physical and email addresses, phone numbers, credit reports and relatives’ names; and “swatting,” or placing fake emergency calls to draw SWAT responses to the victims’ homes.

U.S. District Judge Kimba M. Wood of Manhattan in March sentenced Islam to one day in prison for computer-related identity theft crimes after he was caught in an FBI undercover operation and arrested the day after he turned 18.

Separate from those offenses, Islam committed crimes to which he pleaded guilty last July in Washington in the case that was unsealed Monday. Other conspirators include four younger individuals in Southern California, Fredericksburg, Va., and Finland linked to websites named exposed.su, exposed.re and exposed.ws, prosecutors said.

Victims of harassment linked to Islam’s group include a University of Arizona cheerleader, identified only by her initials, with whom Islam was infatuated. Islam’s March 22, 2013, bogus report of a shooting and a “man with a rifle” armed with explosives prompted a four-hour plus lockdown of the university’s administration building and a campus evacuation.

Islam also communicated a false bomb threat at the White House on April 23, 2015.

For Hollywood targets, Islam also contacted the celebrity media site TMZ for coverage. TMZ reported on some of his group’s online postings and police calls to celebrities’ homes.

On April 27, 2013, police in Montgomery County, Md., responded to a bogus report of a person shot at Blitzer’s residence near the Congressional Country Club in Bethesda. They later established with the network that he and his wife were in New York at the time.

Mark Dycio, an attorney for a Virginia victim identified as W.L. and a leader and promoter of the National Rifle Association’s Freedom’s Safest Place campaign, told the court his client wanted to attend the hearing but was the target of “constant death threats.”

On April 4, 2013, a member of Islam’s conspiracy targeted W.L. in opposition to his “opinions on the issue of gun control” and told police that W.L. had shot his wife and would shoot police. Dycio said his client was on the phone with police trying to clear up the matter when he walked outside his home with his wife holding a cellphone in his hand.

“Consider the irony,” Dycio said, “if a police officer had shot [him] despite the fact that [he] has promoted” protecting police from violence.