His hands cuffed in front of him, a 25-year-old man stood in a prisoner's box Thursday and signed over his business affairs to a power of attorney.

Eric Lu's charge of first-degree murder marked the third and apparently final arrest in the death of his 59-year-old mother, Mississauga businesswoman Ming-Chien "Teresa" Hsin.

Sitting in the body of the courtroom for Lu's first appearance was a man who identified himself as Lu's "good friend," a man who Lu lived with before and since his mother was killed.

"These two were really close. I'm not kidding you. It doesn't make sense," the man said in an interview, declining to give his name. "He loved his mother very much."

In November 2014, it was Lu who called 911 when his mother stumbled home, bloody and near death, having been stabbed in the underground parking lot of her Mississauga home.

Lu survived that attack and no charges were laid, but police say that stabbing forms part of their ongoing investigation into Lu's murder five months later.

"It seems rather silly that you would call 911 to save your mother and then five months later, to take her out," Lu's friend said. "It doesn't make sense."

But regardless of who police think was behind the 2014 attack, investigators say they are confident the evidence in Hsin's death points to her son.

"We started following the evidence and it became evident early on as to what we were looking at," Peel Regional Police Homicide Insp. George Koekkoek said at a news conference Thursday.

Investigators had to rule out several other possible motives before landing on Lu and two other men. Because of some seemingly shady business dealings, Hsin, it seemed, had several people in her life who may have wanted her dead.

A passerby noticed Hsin slumped over in her car in a Mississauga parking lot April 10.

"Ms. Hsin had been reported missing to Peel Regional Police's 12 Division two days prior on the evening of April 8th by her son Eric Lu," Koekkoek said.

While police remained tight-lipped on the case publicly, they were busy working the investigation behind the scenes.

According to Lu's friend who spoke on condition of anonymity, Lu thought police may have been narrowing in on him.

"Eric talked about it. He said, 'They're trying to implicate me in this,'" the friend said.

Lu was arrested at his home Wednesday without incident. His arrest came on the heels of two other men.

Toronto man Mark Dookhram, 21, was arrested on one count of first-degree murder Monday. He seemingly had no direct connection to Hsin. The following day, 25-year-old Justine Ordonio -- a friend of Dookhram and long-time friend of Lu -- was arrested on the same charge. Lu was arrested one day later.

Police would not comment on why they believe Hsin was killed.

Hsin was an entrepreneur who in recent years opened a chain of Relaxology Wellness Centres across the GTA. Her son played a role in the business, but, according to his friend, "Upon her death, he wanted nothing to do with that business. He wanted nothing to do with Relaxology...He just wanted his mother."

"There was no insurance. There was no life insurance whatsoever," the friend said. "He (Lu) had a lot more to lose from his mother's death than he had to gain."

Before his arrest, Lu was raising money for a business of his own -- a business he said would be the first in Canada to sell hydroponically-grown grass to pet owners in condos and apartment buildings.

Investigators would not comment on the roles they believe the three men played in Hsin's murder, revealing for the first time Thursday the cause of death: multiple stab wounds.

"We laid the charge of first-degree murder because we believe that this was a planned and deliberate act and that it was pursuant to an agreement between the three parties to cause the death of Ms. Hsin," Koekkoek said.

The Homicide boss wouldn't say what investigators believe the terms of that agreement were.

Lu was remanded into custody following his court appearance Thursday. He is scheduled to appear back in the Brampton courthouse via video in December.