Teenager Heather Mack made worldwide headlines when she and her boyfriend allegedly beat her mother to death and stuffed her body into a suitcase in the back of a Bali cab – but the violent outburst came as no surprise to friends, The National ENQUIRER has learned.

We discovered that Heather, 19, had a long history of violence in Chicago before she and her 21-year-old boyfriend, Tommy Schaefer, were reportedly caught after loading a cab with a blood-stained suitcase 
containing the mutilated, half-
naked, body of 62-year-old Sheila von Wiese-Mack.

The couple are now being held for trial in a jail in Indonesia, where complex laws mean they haven’t been formally charged – and yet could face death by a firing squad.

And while the cold-blooded killing startled many around the world, Heather’s troubled relationship with her mom was well documented in Oak Park, an 
upscale Chicago suburb, where the Macks had lived most of their life. Sheila and Heather had been seen battling many times – with police being called to their home on domestic disputes an astonishing 86 times!

“Heather was a wild child,” close friend Alex Rivera, who attended high school with Heather and Tommy, told The ENQUIRER in an exclusive interview.

“He knew she was battering her mom and he was trying to help her with her problems. Tommy was a good kid. She ruined his life.”

One family friend called the relationship between the two women “difficult,” and another revealed she had seen mother and daughter have a violent argument outside the local high school.

“I was worried about Sheila,” said Laura Voigt, recalling the incident.

Sheila, an academic who once worked with Ted Kennedy and studied with famed author Saul Bellow, was also seen arguing heatedly with Heather and Tommy over their Bali hotel bill just one night before she was found in the blood-soaked suitcase.

Weeks earlier at a Chicago hotel suite, party-hearty Heather had run up a $1,000 room-service bill – on Sheila’s credit card. The booze-soaked bash, which Tommy taped, ended in him being busted on a disorderly conduct charge.

One schoolmate says Heather was “anti-social and always a little strange,” adding that she fought with students and had dropped out of two different schools.

Another said: “I have absolutely no idea what Tommy saw in Heather or what might have brought him to participate in a murder.”

Pals now wonder if they might have missed an ominous warning.

On July 20, Tommy posted a chilling Facebook status: “Leaving Aug. 4th for Indonesia… might not come backkkk.”