Four members of YouTube’s “Trollstation” were sentenced on Monday after pleading guilty to using threatening, abusive, or insulting behaviors with the intent to cause fear, the BBC reports. The charges refer to two pranks they pulled—a fake robbery at London’s National Portrait Gallery and a fake kidnapping at Tate Britain.

The four members, all of whom are in their twenties, will serve between 24 and 28 weeks. A fifth member was sentenced to a total of 36 weeks in March for his involvement in the fake robbery as well as a separate bomb hoax.

“The hoaxes may have seemed harmless to them,” Robert Short from the Crown Prosecution Service told the BBC, “but they caused genuine distress to a number of members of the public, who should be able to go about their daily business without being put in fear in this way.” He added that the convictions are meant to “send a strong message” that these unlawful activities won’t be tolerated.

A member of the group told the BBC that their aim “was never to get away with breaking the law.” He said that the group tries to use its influence positively, and will consider reevaluating its approach.