Police officers and their vehicles line the street outside the house of one of the suspects in a mass shooting in Redlands, California December 2, 2015.

The U.S. Justice Department’s wide-ranging effort to prosecute so-called “lone wolf” individuals seeking to support ISIS moved ahead on Thursday in Pennsylvania, New York, Kansas and San Bernardino, California, where 14 people were killed this month.

A Pennsylvania teenager was arrested after investigators said he tried to help individuals travel to the Middle East to join the militant group.

Meanwhile, a New York man pleaded guilty in a separate case to terrorism-related charges, admitting that he also tried to recruit individuals to travel abroad to fight for ISIS, which controls territory in both Syria and Iraq.

In a third case, a Kansas man appears set to plead guilty after being charged with plotting to set off a suicide car bomb at a U.S. Army installation, according to court records.

Federal authorities have arrested more than 70 people since 2014 for planning to aid ISIS.

The couple who carried out the deadly Dec. 2 mass shooting in San Bernardino were inspired by the militant group, authorities said.

Prosecutors in Los Angeles on Thursday charged Enrique Marquez, a longtime friend of one of the shooters, Syed Farook, with plotting attacks in 2011 and 2012 and with illegally buying the rifles the couple used in their assault.

The Pennsylvania and New York cases highlight Islamic State’s aggressive use of social media to inspire followers.

Jalil Ibn Ameer Aziz, 19, of Harrisburg, Pennsylvania, used at least 57 Twitter accounts to advocate violence against Americans, disseminate ISIS propaganda and post the names of U.S. military members that he said should be targeted, prosecutors said.

Aziz also used the accounts to help individuals seeking to travel to Syria to fight for ISIS, according to a criminal complaint. Authorities said Aziz had ammunition, several high-capacity weapons magazines and a knife in a tactical-style backpack in his closet.

The New York man, Mufid Elfgeeh of Rochester, 31, used 23 Facebook accounts to distribute ISIS videos and recruit two individuals to travel to Syria to train as fighters, according to his plea agreement.

On Wednesday, Federal Bureau of Investigation Director James Comey said ISIS had “revolutionized terrorism” by employing social media networks to reach followers across the globe.

Other militant groups still manage to draw potential followers from the United States, as well.

Prosecutors announced on Thursday the indictment of a 22-year-old California man, Adam Shafi, for attempting to travel to Syria to join the al-Qaeda-linked group al-Nusrah Front.

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