Sarah Olson talked to reporters just one day after the woman accused of killing him, Theresa Balboa, was charged with capital murder.
When asked about the message she had for Balboa, Sarah said, "I have no words for her."
Balboa, 29, was the girlfriend of Samuel's father, Dalton.
NOTE: Some details of the case may be disturbing. Viewer discretion is advised.
According to new court documents, Balboa hit Samuel with an object, but it's unknown what that object was.
Investigators say Balboa reported the 5-year-old missing and pretended to look for him days after she killed him and hid his body in storage.
Officials determined Samuel died by homicidal violence. The cause of death was blunt head trauma.
Police say Balboa eventually moved Samuel's body two hours away from Houston to Jasper.
"I'm thankful that someone is finally being held accountable for my son, and I'm hoping more justice gets served," Sarah said, adding that she believes Dalton should be charged as well.
Police have not said Dalton was involved in his son's death. Dalton said Balboa had been babysitting Samuel since April 30. That has also been confirmed as the last day that Samuel was in school.
"He was supposed to keep our son safe, and he didn't. He took him away from me. For what? To have him murdered?" Sarah said. "Honestly, the person that I feel really needs to be charged is still walking around and that's really what I'm waiting for."
Sarah said that Dalton tried to contact her about a week after Samuel's body was found, but she did not answer his phone calls.
Two more people connected to Balboa have also been charged: her roommate Benjamin Rivera and her friend Dylan Walker.
Both men are charged with tampering with evidence.
Rivera, 27, is accused of helping Balboa hide Samuel's body. He told police that it was about May 10 when Balboa called him to say Samuel was dead.
According to court documents, Rivera came home to their apartment in the 15600 block of the Gulf Freeway and found Samuel bruised and unresponsive on the bed. He further told police that he and Balboa put the boy's body in the bathtub and left him there for two days.
On May 13, Rivera says he bought duct tape and a plastic box from a Walmart, and that he and Balboa wrapped up the child's body, placed it in the box and took it to a storage unit on Highway 3 in Webster.
Meanwhile, Walker is accused of driving Balboa to Jasper. He called Crime Stoppers to report what happened.
Sarah spoke publicly for the first time nearly a month ago. She was asked at the time what she missed most about her son.
"Having him. He was sweet. He was very obedient. He was definitely a mama's boy," she told reporters.
Olson explained the last time she saw Samuel was for his 5th birthday in May 2020.
"When I got there, he told me, 'I knew you would come for me.' You know, he just basically stood with me the whole time. And I was planning on taking him home that day but I was stopped," she said.
Sarah credited her strong faith in God for helping her to get through her son's disappearance, and now, murder.
"The prayers. My prayers. Y'all's prayers. I believe that really is getting me through this," she said. "Other than that, I don't know. I don't know how I'm standing here talking to you. I don't know how I'm processing it other than I have faith in God."
Sarah revealed Friday that Samuel's body had been cremated. A private service will be held for him on Saturday.
"I was waiting so long to get my son back. This isn't how I wanted to celebrate him coming back, so it hurts. It hurts having to do this because it wasn't supposed to be like this," she said.
"Don't stop fighting for your babies," she added as a message to parents. "Do whatever it takes, just make sure they're safe."
Balboa is due in court on Monday for the capital murder charge.
SAMUEL OLSON COVERAGE