A Perth teenager allegedly murdered whilst meeting up with people he encountered on a gaming website was found buried in a shallow grave under a newly-laid concrete slab, police have said.

Aaron Pajich, who had Asperger's syndrome, was last seen about 9.30am on Monday last week at the Rockingham City Shopping Centre taxi rank where he was due to meet a woman, and a man only known as Daniel.

The heartbreaking words from Aaron’s parents, Keith Sweetman and Sharon Pajich, come after two women were charged with the 18-year-old’s murder.

The women, aged 42 and 25, are due to face Perth Magistrates Court on Thursday...

Detective Senior Sergeant Dave Gorton, of Major Crime, told media on Wednesday that one of the women charged studied at the same educational facility in Kwinana as the 18-year-old.