Updated – December 8, 2014 11:43 a.m. ET

Samaria Rice, speaking at a news conference in Cleveland on Monday, revealed new details from the day her 12-year-old son Tamir Rice was shot by a police officer.

Rice said that when she got to the park where her son was shot, she found her 14-year-old daughter, who was also at the park that afternoon playing, handcuffed in the back of a police car. When Rice later reunited with her daughter, the young girl said police officers tackled and handcuffed her once she saw her younger brother lying on the ground, bleeding.

When Samaria arrived and saw her youngest child shot and her daughter in the back of a police car, police officers warned her that if she didn't calm down, she'd be placed in the police vehicle as well.

The family's attorney, Benjamin Crump, argued that if there is enough probable cause, "we don't need to have another grand jury."

"There is nothing written in the law that police officers should be treated differently from other citizens," Crump said. "It's an unwritten rule we've accepted. You can charge the officer." He has also represented the family of Michael Brown in Ferguson, Missouri, and Trayvon Martin in Florida.

Rice repeated what she said this morning on Good Morning America, stating that she is looking for a conviction of the two officers involved in the shooting.

"The family is very distrustful of whether local authorities will indict a police officer," Crump said.

Rice's 12-year-old son Tamir was shot by Officer Timothy Loehmann on Nov. 22 outside Cudell Recreation Center in Cleveland. He was playing with a pellet gun. Surveillance footage from the park shows that once the police officers arrive, Loehmann shoots the boy seconds after confronting him.

The mother said at the news conference that she didn't allow toy guns in the house and that Tamir got the pellet gun he was playing with on November 22 from a friend.

Earlier in the day, she said on Good Morning America that she wants to see both police officers involved in his shooting be held accountable. "I'm looking for a conviction," she said on Good Morning America.

"Tamir was a bright child," Rice said. "He had a promising future. He was very talented in all sports and he was just a wonderful kid. Everybody loved him. He was my baby."

The Rice family filed a federal wrongful death lawsuit alleging excessive force, assault, and battery.

"The family is focused on getting justice for Tamir," Crump said on GMA. "They're very concerned because they look at what happened in the [Eric] Garner case, where there was no indictment when a man was choked on video … They are very concerned about local prosecution."