AN internet troll who targeted the grieving families of dead teenagers has been jailed.

Sean Duffy, 25, targeted Facebook tribute pages and posted videos on YouTube taunting the dead and their families.

One of his targets was Natasha MacBryde, 15, who threw herself under a train after suffering bullying.

Duffy, who is unemployed and did not know any of his victims, posted an anonymous video on YouTube called Tasha the Tank Engine, which her family said left them feeling "shocked, outraged and physically sick".

He pleaded guilty to two counts of sending malicious communications relating to Natasha.

He asked for three other cases of Facebook trolling to be taken into consideration when he appeared before magistrates in Reading, southern England.

Joanne Belsey, prosecuting, said Duffy's attacks began after the death of 16-year-old Hayley Bates, who died in a car crash in September 2010.

He defaced pictures of her and wrote underneath a picture of flowers at the crash site: "Used car for sale, one useless owner."

He also created a Facebook page entitled RIP Lauren Drew after the 14-year-old died from an epilepsy attack. He posted images called "Lauren's epifit" and "Lauren's rotting body". For Mother's Day he created a YouTube video with a picture of a coffin saying "Happy Mothers Day".

His final target was Jordan Cooper, 14, who was stabbed to death. He created a group called "Jordan Cooper in pieces" that had a profile picture of a bloodied knife.

Jailing Duffy for 18 weeks, the maximum possible sentence, the chair of the bench, Paul Warren, said: "You have caused untold distress to already grieving friends and family.

"The offences are so serious only a custodial sentence could be justified."

He went on to say that the case served as an illustration of the "harm and damage" that malicious use of social networking sites could do.

Duffy was banned from social-networking sites for five years. He will also have to inform police of any phone he has or buys that comes with internet access.

Lauren Drew's father, Mark, spoke outside court and described the family's pain.

"We were already having a hard time," he said. "These children live on Facebook and they are so vulnerable. Even after Lauren died, she was still vulnerable."

Tthe court heard that Duffy has Asperger's syndrome and suffers with alcohol problems.