(CNN)Precious little is known about how exactly Freddie Gray died.
The 25-year-old Baltimore resident was arrested on April 12, fell into a coma, and died one week later from a fatal spinal cord injury. An investigation is underway.
The six officers involved in Gray's arrest have been suspended with pay, but -- so far -- none has spoken about the incident publicly.
A person close to one of the officers approached CNN and, on the condition of anonymity, agreed to give that officer's account. The source said the officer did not request the interview.
According to the source, the officer believes Gray was injured while he was being arrested, but before he was put inside a police van. The officer does not know how Gray was hurt, the source said.
Cameras recorded parts of his arrest. Gray, handcuffed and screaming in apparent pain, was lifted off the ground by officers, who dragged him to the van. He was conscious and talking.
At one point after it left, the van stopped and Gray was placed in shackles.
"Freddie Gray was shackled because he was irate. He was irate; he was angry. He was moving around in the wagon so they were asked -- the arresting officers were asked to leg shackle him, and that's when the wagon pulled over," the source said Wednesday.
The source also said Gray was not seat-belted in the van, and gave an explanation as to why.
"They didn't want to reach over him. You were in a tight space in the paddy wagon. He's already irate. He still has his teeth and he still has his saliva. So, in order to seat belt somebody you have to get in their personal space. They're not going to get in his personal space if he's already irate.
"Most people in the paddy wagon aren't seat belted in. They are just now starting to seat belt as a result of this case," the source said.
The Baltimore Police Department has identified the six officers involved in Gray's arrest as: Lt. Brian Rice, 41, who joined the department in 1997; Officer Caesar Goodson, 45, who joined in 1999; Sgt. Alicia White, 30, who joined in 2010; Officer William Porter, 25, who joined in 2012; Officer Garrett Miller, 26, who joined in 2012; and Officer Edward Nero, 29, who joined in 2012.