11/12/2015 13:21 EST | Updated 11/12/2016 00:12 EST

Teresa Hsin murder: Son played role in 'deliberate and planned' killing

Eric Lu was the one who reported his mother missing, but now he's charged with her murder, Peel Regional Police said on Thursday.

Ming-Chien (Teresa) Hsin, 59, was found stabbed to death in her black BMW SUV in a Mississauga parking lot in April. Just two days before, Lu — her only child — had reported her missing to police.

Lu, along with two others, were arrested and charged with first-degree murder in connection with Hsin's death following a seven-month long investigation this week. All three are from Toronto.

"We believe the murder was deliberate and planned and pursuant to an agreement between the three … but I can't get into the exact details," Insp. George Koekkoek told reporters at a media conference on Thursday, noting the case is now before the courts.

Koekkoek wouldn't say who directed the killing or what motivated the crime.

"I can't speak to motive at this time," Koekkoek said.

Hsin owned a chain of successful spas across the GTA, and according to Lu's Facebook page her served as the company's CEO.

Police confirmed Lu was involved in the business, but couldn't confirm his role. Nor would Koekkoek say what Lu stood to gain from his mother's death.

Hsin was also the victim of a knife attack in an underground parking garage near her home six months before her death, though police are still trying to determine if that incident is connected to her killing, Koekkoek said. No charges were ever laid in that case.

Also charged are: Mark Dookram, 21, and Justine Ordonio, 25.

"These are serious charges," said Peel Regional Police Const. George Tudos.

"There is strong evidence against these three accused."

Police said they have no information that anyone else is involved in Hsin's death at this time.