U.S. President Barack Obama arrives with Fraternal Order of Police National President Chuck Canterbury, right, at the National Peace Officers' Memorial Service at the U.S. Capitol in Washington, D.C., May 15, 2015. Reuters

Electronic files of the Fraternal Order of Police — the United States’ largest police union — were hacked Thursday, revealing a series of forum posts criticizing President Barack Obama, Supreme Court Justice Sonya Sotomayor and undocumented immigrants, the Guardian reported. The names and addresses of officers as well as various contracts between police agencies and the cities they are located in were also released in the data dump. By early Friday afternoon, the FOP’s website was offline.

The FBI is investigating the hack, and the head of the FOP, Chuck Canterbury, said while some information was taken, more sensitive information such as financial details were most likely not compromised.

“Some names and addresses were taken,” Canterbury said. “It concerns us. We’re taking steps to try to notify our members but that is going to take some time.”

One 2010 post from a private forum by someone who went by the name of Robert Schafer wrote Obama was both anti-police and anti-law and order. Another post, from 2009, called Sotomayor a radical socialist, and said FOP officials shouldn’t have endorsed her.

Police unions, including the FOP, have been highly critical of Obama in the wake of the high number of police-involved shootings of civilians in the past two years, including the killing of Michael Brown, who was black, by a white police officer in Ferguson, Missouri, which sparked national protests, the Hill reported. Obama said after said after the Ferguson unrest there was no excuse for violence against police officers, but that there is also no excuse for police to use excessive force.

Contracts that numbered in the hundreds were also released in the data dump, some of which have been scrutinized in the past year in the wake of the officer-involved shootings. Some groups have criticized the contracts for making it more difficult to prosecute police officers involved in these shootings, the Huffington Post reported.