A 20-year-old woman has been charged with second-degree murder for allegedly kicking her boyfriend's 17-month-old son to death.

Alicia Goemaat, from West Seattle, Washington, is accused in the death of Drue Lehto, whom she was looking after as his dad, Derek, ran errands on September 27.

Derek's mother, Maria Blanco, told INSIDE EDITION that her son is in shock.

"He just keeps crying, 'She killed my little boy! She killed my little boy!'" she said. "We knew the baby as being a healthy, happy little guy. We're in a state of disbelief."

Read: Baby Reportedly Chokes to Death After His Mom Dies While Feeding Him

Goemaat, who has a two-year-old son of her own, told cops that she became angry when the toddlers started fighting over a toy, according to the Seattle Post-Intelligencer.

She said that on September 27 she kicked Drue in the stomach, knocking him to the ground, according to reports. She reportedly said she kicked him again before putting him in his playpen, where he was later found unresponsive.

After the boy's father arrived home, he tried to administer CPR but the youngster passed away before medical staff arrived, according to Seattle PI. An autopsy found that he died of abdominal trauma and internal bleeding, and the Medical Examiner's Office ruled his death a homicide.

Goemaat denied knowing what happened to him until she was arrested days later, on October 1, according to reports.

Drue's grandmother, Maria Blanco, told INSIDE EDITION that she saw her son and Goemaat, who had been dating for about four months, the day after the boy's death.

"She didn't even look me in the eye," Blanco said. "Nothing came out of her mouth."

Blanco said she previously thought Goemaat was "odd" but that she had never seen the young woman direct any anger towards Drue.

An ex-boyfriend also told KIRO that he never saw Goemaat act violently, and couldn't believe she was capable of the crime.

"She never seemed like a violent person to me," Josh Bryant said. "She was never rough with my kids, or her kid, or anyone else’s kid."

Story continues

Blanco said her son, 30, is now trying his best to cope.

Read: Prosecutors: Man and His Girlfriend Dismembered His 16-Year-Old Stepsister in Sexually Motivated Attack

"He still drops to the ground in disbelief," she said. "Derek was a good father to that little boy... That little baby was Derek's life and his light. He was always making sure he had the best."

"We've never been through anything so hard," she added.

Blanco said they plan on going to Goemaat's arraignment on October 20. Goemaat remains held in King County Correctional Facility in Seattle on $1 million bail, according to online jail records. She does not have a lawyer listed.

"I hope she gets the maximum," Blanco said.

She and her husband set up a fundraising page to help pay for Drue's funeral costs.

"We are so thankful for the short time we had with our little precious angel Drue," they wrote on the page.

Watch Below: Mother Kills 17-Month-Old Daughter After Giving Her Methadone

Related Articles: