HOUSTON, Texas (KTRK) -- As the second person charged in the death of 5-year-old Samuel Olson posted $100,000 bond on Thursday, the chief prosecutor in the case revealed that a weapon that may have been used to kill the boy has been located.
Ben Rivera faced a judge Thursday morning as he heard the conditions of his bond.
Authorities say the 27-year-old was the roommate of Theresa Balboa, who is also charged with the same tampering charge.
Rivera is accused of helping Balboa hide the lifeless body of the 5-year-old boy, who is the son of Balboa's boyfriend.
On top of being ordered to house arrest, Rivera was banned from the use of firearms, as well as being in contact or around children and family members of Balboa or Olson.
After Thursday's hearing, Andrea Beall, the chief felony prosecutor in the case, said Rivera is cooperating with homicide investigators at the moment, though they are trying to verify his statement with the evidence in the case in order to make sure he's trustworthy.
Beall also revealed that they believe they found the weapon that may have led to the boy's death. No specifics were given as to where the weapon was found. Additional testing is being performed on it to confirm whether it was used to killed Samuel.
Shortly after Rivera made bond, Tonya Olson, the boy's grandmother issued the following statement Thursday afternoon:
"We are vey disappointed! That the bond was so low. And our hearts are broken that he gets to walk around free and Sammy can't!"
Details about Rivera's alleged involvement and what led to his charge
Samuel was found dead in a plastic container wrapped in a tarp and duct tape in a Jasper motel room on June 1, along with his father's girlfriend, Theresa Balboa.
Balboa is being held on a $600,000 bond.
During an interview with Rivera, police investigators say he told them he received a call on May 10 from Balboa saying Samuel was not breathing and telling him to come home.
Houston police investigators say the 27-year-old told them he returned to their apartment in the 15600 block of the Gulf Freeway in Webster that day and saw the child unconscious with bruising on his body. He said they placed Samuel's body in the bath tub where he stayed for two days.
Rivera told police he went to Walmart on May 13 and bought duct tape and a plastic tote bin that they put the child in and took him to a storage unit where he remained until May 31. Court records say investigators found the Walmart receipt during a search warrant, according to records.
After an extensive investigation, court documents say police found evidence conflicting the timeline Rivera gave them.
During a search of his phone, investigators found a text message from Balboa to Rivera on May 5 saying that she needed to speak to him before he came inside the apartment.
On May 12, court documents say Balboa sent a text to Rivera saying she was going to move Samuel's body to the bed, after learning from Rivera that the apartment's maintenance would be entering their unit that day.
WATCH: Reporter Notebook: Covering the death of Samuel Olson
Surveillance video from a storage facility in Webster shows Rivera's truck with the bin Samuel's body was later found in, in the back arriving on May 22.
Evidence that has been recovered by police in the weeks following the 5-year-old being reported missing disproves the original report about what happened to the child.
In court documents released earlier this month, investigators wrote Balboa claimed that at about 7:30 a.m. on May 27, Samuel's mother, Sarah Olson, arrived at Balboa's home with another man and took the little boy without permission.
Sarah, however, provided authorities surveillance video from her home to show she couldn't have taken the child. While authorities and volunteers with Texas EquuSearch combed a field looking for signs of Samuel the following Monday, authorities now believe the little boy had already been dead for weeks.
The medical examiner ruled that Olson died from blunt trauma to the head.
Balboa is not due back in court until July.
Although Balboa and Rivera are both charged with tampering with evidence in the case, no charges have been filed for the child's murder.
WATCH: Will doctors be able to determine how Sam Olson died?