Nov. 19, 2009  -- A 15-year-old boy who was killed by his father in an execution style killing spent the last moments of his life pleading, "No, Daddy! No!"

Jamar Pinkney Jr. was shot in the head Monday by his 37-year-old father, Jamar Pinkney Sr., who allegedly made the teen strip his clothes off and kneel in a vacant lot before he was killed by a single bullet.

The boy's mother, Lazette Cherry, told the Detroit Free Press that Pinkney Sr., showed up at her Highland Park, Mich., home after she told him that their son had made a startling confession.

According to Cherry, the 15-year-old had admitted to having "inappropriate contact" with his 3-year-old half sister.

"I called and told his father this isn't something you sweep under the rug," Cherry, who was unable to be reached by ABCNews.com, told the paper.

Pinkney Sr. began by pistol whipping his son in the living room where the teen lived with his mother before taking him outside, despite Cherry's pleas to stop.

The father marched the naked boy into the lot and made him kneel down. As the boy pleaded for his life and his distraught mother looked on, Pinkney Sr. allegedly executed the boy with a shot in the head.

Pinkney Sr. was charged with first degree murder and if convicted, could spend the rest of his life in prison. The judge entered a "not guilty" plea on behalf of Pinkney. He is also charged with three counts of felonious assault and one count of felony firearm.

Video of the arraignment shows a relative of the child being taken out of the court room after screaming "No, no, no," when Pinkney Sr. was led into court.

His lawyer, Corbett O'Meara, called the incident a "devastating tragedy."

"My client is in shock and in mourning, but is hopeful that his family will be able to come out of this in as whole a state as possible," said O'Meara.

O'Meara said that Pinkney Sr., who turned himself into authorities, had no previous criminal history and had worked "for years" as a letter carrier for the United States Post Office.

Boy Killed by Father Was Known as Teddy Bear

"No individual has the right to exact the death penalty on another no matter how reprehensible the behavior," prosecutor Kym Worthy said in a statement. "That is why we have laws."

O'Meara told ABCNews.com that he hopes Worthy will "realize the case is far from straight forward" and requires something "other than the most aggressive" punishment.

And even though Pinkney Sr. had never been diagnosed with mental health problems, O'Meara said that if the allegations of the murder are true, "there must be issues with his mental health."

Meanwhile, the community where the child was raised is mourning the loss of a boy they say was known by friends as "teddy bear."

Volunteers at the high school where Pinkney Jr. was a sophomore said the teen was "always smiling," according to The Detroit News.

The principal at Martin Luther King Jr. High School, Deborah Jenkins, told the paper that Pinkney Jr. was "well-liked" and that the school community has been "shaken badly" by his death.

"He was articulate. He passed his courses with A's, B's and C's. Everyone knew him to be a nice, quiet boy," said Jenkins.