A rise in domestic extremism has U.S. law enforcement officials scrambling to keep up. Currently, the FBI has 850 active investigations into domestic terrorism, up from last year, a top counterterrorism official told Congress on Wednesday. Officials couldn’t compare it to a year before but, when asked, said the number was definitely trending up.

“The velocity in which we are working our cases, both on the domestic terrorism side and the international terrorism side, with homegrown violent extremists, that velocity is much quicker than its ever been before,” Michael McGarrity, assistant director of the FBI’s Counterterrorism Division, told the House Homeland Security Committee.

Just last week, a 19-year-old man opened fire in a California synagogue, killing one person and wounding three more in an attack believed to be an anti-Semitic hate crime. That follows the April burning of three black churches in Louisiana under suspicious circumstances, the October attack on a Pittsburgh synagogue that left 11 dead, and more avowed or suspected hate crimes.

The number of white supremacist groups rose to a record 1,028last year, according to the Southern Poverty Law Center. The ability of hate groups to motivate and radicalize people online was a key point of concern to McGarrity and the other government officials who testified on Wednesday.