Story highlights The woman is a 51-year-old great-grandmother

Her injuries are severe, her lawyer says

Police: "Tape only shows small part of what transpired"

The family of a 51-year-old woman shown in a video being repeatedly punched by a California Highway Patrol officer says they plan to sue the agency.

"How do I know he's not going to hurt me or anyone else?" the woman's daughter, Maisha Allums, t old reporters Sunday . "So I am just here with a voice for my mom and everyone else."

The beating took place Tuesday along the Santa Monica freeway and was caught on tape by passing motorist David Diaz.

"This is not just jabs, they are hooks," he said. "Those are lights-out punches. Those aren't like taps.

"You see it, you heard it. It was like 'thump, thump, thump' and then you see her head bouncing 'bam, bam' on the concrete. Then you hear her screaming, 'No, don't, stop.' Then you even -- at the end where she has her hands up like this -- when it's clear there is no more resistance, he takes another four or five shots."

The woman who was beaten is Marlene Pinnock, a great-grandmother.

Caree Harper, the lawyer who is now representing her, says Pinnock's injuries are severe.

"Her family went to visit her," Harper said. "She has multiple lumps in her head, lumps on her shoulder like the size of a plum, bruises and lumps all over her upper body."

A police report released Friday says the woman posed a danger to herself and other drivers because she was "walking within traffic lanes" at times.

It also says that when an officer asked her to stop, she "continued ignoring the officer's command" and ultimately she "becomes physically combative."

"The tape only shows a small part of what transpired," California Highway Patrol Assistant Chief Chris O'Quinn told reporters. "There are events that led up to this. Until all that's collected and put into perspective we aren't going to be able to make a determination,"

The agency didn't identify the officer, but says he has been put on paid administrative leave.

"The CHP, to justify the beating, (are) saying they were trying to protect her from harm," Harper said. "With a beating like that no one wants to be protected. She only needed protection from the officer."

Pinnock is in a hospital under an involuntary psychiatric hold.

Harper says a hearing will take place Tuesday to determine whether she will remain in custody longer.

"We are concerned she's still being involuntarily kept at a facility," she said.