Sandra Layne
© WDIVM
Sandra Layne
A Michigan grandmother has pleaded not guilty after she was charged with murdering her 17-year-old grandson by shooting him the chest eight times.

Bloomfield Township Police Detective Brad Boulet testified on Monday that Jonathan Hoffman called 911 and begged them to help, saying he had been shot in the chest by 74-year-old Sandra Layne and was going to die. Hoffman screamed while on the phone with dispatchers and said he had been shot again, according to the Detroit Free Press.

When officers arrived on the scene, the grandmother came to the door holding .40-caliber Glock handgun in her right hand.

"While walking toward the officers, Ms. Layne exclaimed that she had just murdered her grandson," Boulet recalled.

It was not immediately clear what had triggered the shooting, but Assistant Prosecutor Jason Pernick suggested that Layne may not be competent to stand trial. Bloomfield Police Lt. Tim Diamond said that she had not yet talked to investigators.

In late March, police were called to the Layne's home over a dispute with her grandson. Hoffman was seen in the street screaming but no charges were filed at the time.

"This young man has been in trouble and my understand is there were apparently some narcotics in the house and some other drugs," Layne attorney Mitch Ribitwer told WDIVM. "He was derogatory towards his grandmother, he was yelling and shouting, he almost got into it with the police. So, I have to say there are some issues with this young man."

Hoffman had moved in with his grandmother to attend an alternative high school in Michigan. His father, Michael, who is a prominent divorce attorney in Scottsdale, Arizona, said that Layne had no reason to use deadly force against an unarmed boy.

"I'm not saying he was aggressive, but if he was, I don't understand how being aggressive but unarmed would justify her using deadly force," Michael Hoffman said.

Hoffman's aunt, Judy Metzger, told the Free Press that the whole family was still in shock.

"He was murdered in cold blood - he was executed," Metzger said. "It's senseless."

"We obviously don't know what (prompted) this woman, who purchased the gun 30 days ahead of time - a shoot-to-kill weapon," she added. "Obviously, the issue lies with her mental facilities. He was just a kid being a kid. Applying and getting summer jobs. He was just getting ready to go to the movies. Of course we don't understand."

Hoffman's funeral was scheduled for 11 a.m. on Tuesday.

On Monday, Judge Marc Barron ordered Layne to be held without bond. She is scheduled to appear at a preliminary hearing on Thursday.

Watch this video from WDIV, broadcast May 21, 2012.